logging: The mismatch of timing of replaceing the Rails default logger with Google::Cloud::Logging::Logger

## Overview

When`Logging.configure.set_default_logger_on_rails_init` is `false`
various loggers in Rails framework(such as `ActiveRecord::Base.logger`) will not be replaced with `Google::Cloud::Logging::Logger`.
This may be because it is too late to replace the Rails default logger with `Google::Cloud::Logging::Logger`.

parhaps related: https://github.com/googleapis/google-cloud-ruby/issues/4510

On the other hand, when `Logging.configure.set_default_logger_on_rails_init` is `true`,
it is too early to replace the Rails default logger.
We got an error trying to reference `Rails.logger.level` when `Rails.logger` is uninitialized.

## Detail

When rails app requires [google/cloud/logging/rails](https://github.com/googleapis/google-cloud-ruby/blob/5da8dc88a4c0b6f101043c8b35ec4ae8627f0b31/google-cloud-logging/lib/google/cloud/logging/rails.rb), the cloud logging initializer will be set as `Railtie#initializer`.

This initializer runs `init_middleware`. In `init_middleware` method,

#### 1. If `Logging.configure.set_default_logger_on_rails_init = false`(default)

`set_default_logger` will be called later.

`Google::Cloud::Logging::Middleware` will be loaded into rack middleware. After rack middlewares were build, then `init_callback` will be called, and `Rails.logger` will be replaced with `Google::Cloud::Logging::Logger` in `set_default_logger` method.

However, when `init_callback` is called, various loggers in Rails framework are already initialized and never will be replaced.

for example:
* https://github.com/rails/rails/blob/v6.1.4.1/activerecord/lib/active_record/railtie.rb#L77-L79
* https://github.com/rails/rails/blob/v6.1.4.1/actionview/lib/action_view/railtie.rb#L58-L60

This is perhaps because Rack middlewares are loaded after `Railtie#initializer` .
https://github.com/rails/rails/blob/90357af08048ef5076730505f6e7b14a81f33d0c/railties/lib/rails/application.rb#L48-L59

#### 2. If `Logging.configure.set_default_logger_on_rails_init = true`

`set_default_logger` is called immediately.

https://github.com/googleapis/google-cloud-ruby/blob/5da8dc88a4c0b6f101043c8b35ec4ae8627f0b31/google-cloud-logging/lib/google/cloud/logging/rails.rb#L82

But at this point, `Rails.logger` is undefined, because `init_middleware` is called before initialize_logger.
So `NoMethodError: undefined method `level' for nil:NilClass` is raised here.

https://github.com/googleapis/google-cloud-ruby/blob/5da8dc88a4c0b6f101043c8b35ec4ae8627f0b31/google-cloud-logging/lib/google/cloud/logging/rails.rb#L120

#### Environment details

- OS: [ruby:3.0.2-slim-buster](https://hub.docker.com/layers/ruby/library/ruby/3.0.2-slim-buster/images/sha256-64d8b5be06054b8b4c79b8c01dec6776401552eebaf91f36ee70be3b3d3d0515?context=explore)
- Ruby version: 3.0.2
- Rails version: 6.1.4.1
- Gem name and version: google-cloud-logging (2.2.2)

#### Steps to reproduce

#### 1. If `Logging.configure.set_default_logger_on_rails_init = false`(default)

1. ` bundle exec rails new sample -d mysql --api`
2. `cd sample`
3. `bundle add google-cloud-logging`
4. make some controller/action
5. require in `config/application.rb` before `Bundler.require`
```rb
require "google/cloud/logging/rails"
```
6. configure in `config/environments/development.rb`
```rb
config.google_cloud.use_logging = true
config.google_cloud.project_id = "someproject"
config.google_cloud.keyfile = "/opt/config.json"
config.google_cloud.logging.log_name = "some_name"
```
7. run server and access the url
8. Got log in Cloud Logging: `Started GET "/" for 127.0.0.1 at 2021-12-02 07:34:43 +0000`, but got other logs in local `log/development.log`

#### 2. `Logging.configure.set_default_logger_on_rails_init = true`

9. add `config.google_cloud.logging.set_default_logger_on_rails_init = true` in `config/environments/development.rb`
10. run server, and got Error:
```
/usr/local/bundle/gems/google-cloud-logging-2.2.2/lib/google/cloud/logging/rails.rb:120:in `set_default_logger': undefined method `level' for nil:NilClass (NoMethodError)
from /usr/local/bundle/gems/google-cloud-logging-2.2.2/lib/google/cloud/logging/rails.rb:82:in `init_middleware'
from /usr/local/bundle/gems/google-cloud-logging-2.2.2/lib/google/cloud/logging/rails.rb:59:in `block in '
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/initializable.rb:32:in `instance_exec'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/initializable.rb:32:in `run'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/initializable.rb:61:in `block in run_initializers'
from /usr/local/lib/ruby/3.0.0/tsort.rb:228:in `block in tsort_each'
from /usr/local/lib/ruby/3.0.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
from /usr/local/lib/ruby/3.0.0/tsort.rb:422:in `block (2 levels) in each_strongly_connected_component_from'
from /usr/local/lib/ruby/3.0.0/tsort.rb:431:in `each_strongly_connected_component_from'
from /usr/local/lib/ruby/3.0.0/tsort.rb:421:in `block in each_strongly_connected_component_from'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/initializable.rb:50:in `each'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/initializable.rb:50:in `tsort_each_child'
from /usr/local/lib/ruby/3.0.0/tsort.rb:415:in `call'
from /usr/local/lib/ruby/3.0.0/tsort.rb:415:in `each_strongly_connected_component_from'
from /usr/local/lib/ruby/3.0.0/tsort.rb:349:in `block in each_strongly_connected_component'
from /usr/local/lib/ruby/3.0.0/tsort.rb:347:in `each'
from /usr/local/lib/ruby/3.0.0/tsort.rb:347:in `call'
from /usr/local/lib/ruby/3.0.0/tsort.rb:347:in `each_strongly_connected_component'
from /usr/local/lib/ruby/3.0.0/tsort.rb:226:in `tsort_each'
from /usr/local/lib/ruby/3.0.0/tsort.rb:205:in `tsort_each'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/initializable.rb:60:in `run_initializers'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/application.rb:391:in `initialize!'
from /app/sample/config/environment.rb:5:in `'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/loaded_features_index.rb:100:in `register'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
from /usr/local/bundle/gems/zeitwerk-2.5.1/lib/zeitwerk/kernel.rb:35:in `require'
from /usr/local/bundle/gems/activesupport-6.1.4.1/lib/active_support/dependencies.rb:332:in `block in require'
from /usr/local/bundle/gems/activesupport-6.1.4.1/lib/active_support/dependencies.rb:299:in `load_dependency'
from /usr/local/bundle/gems/activesupport-6.1.4.1/lib/active_support/dependencies.rb:332:in `require'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:54:in `require_relative'
from config.ru:3:in `block in '
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/builder.rb:116:in `eval'
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/builder.rb:116:in `new_from_string'
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/builder.rb:105:in `load_file'
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/builder.rb:66:in `parse_file'
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/server.rb:349:in `build_app_and_options_from_config'
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/server.rb:249:in `app'
from /usr/local/bundle/gems/rack-2.2.3/lib/rack/server.rb:422:in `wrapped_app'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/commands/server/server_command.rb:77:in `log_to_stdout'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/commands/server/server_command.rb:37:in `start'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/commands/server/server_command.rb:144:in `block in perform'
from :90:in `tap'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/commands/server/server_command.rb:135:in `perform'
from /usr/local/bundle/gems/thor-1.1.0/lib/thor/command.rb:27:in `run'
from /usr/local/bundle/gems/thor-1.1.0/lib/thor/invocation.rb:127:in `invoke_command'
from /usr/local/bundle/gems/thor-1.1.0/lib/thor.rb:392:in `dispatch'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/command/base.rb:69:in `perform'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/command.rb:48:in `invoke'
from /usr/local/bundle/gems/railties-6.1.4.1/lib/rails/commands.rb:18:in `'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/loaded_features_index.rb:100:in `register'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
from /usr/local/bundle/gems/bootsnap-1.9.3/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
from /app/sample/bin/rails:5:in `'
from /usr/local/bundle/gems/spring-3.1.1/lib/spring/client/rails.rb:30:in `load'
from /usr/local/bundle/gems/spring-3.1.1/lib/spring/client/rails.rb:30:in `call'
from /usr/local/bundle/gems/spring-3.1.1/lib/spring/client/command.rb:7:in `call'
from /usr/local/bundle/gems/spring-3.1.1/lib/spring/client.rb:30:in `run'
from /usr/local/bundle/gems/spring-3.1.1/bin/spring:49:in `'
from /usr/local/bundle/gems/spring-3.1.1/lib/spring/binstub.rb:11:in `load'
from /usr/local/bundle/gems/spring-3.1.1/lib/spring/binstub.rb:11:in `'
from /app/sample/bin/spring:10:in `require'
from /app/sample/bin/spring:10:in `block in '
from :90:in `tap'
from /app/sample/bin/spring:7:in `'
from bin/rails:2:in `load'
from bin/rails:2:in `'
```

#### Code example

described above

#### Full backtrace

described above