Sidekiq Middleware registered in the wrong order with Batches when used with Sidekiq Pro

When using `activerecord-multi-tenant` with the paid Sidekiq-Pro gem, sidekiq [batch callbacks](https://github.com/sidekiq/sidekiq/wiki/Batches#callback-details) do not have a tenant set by default, even if the original job and batch were enqueued inside a tenant block.

Given the following example job:

```ruby
class TestJob
include Sidekiq::Job

def perform
puts "perform"
puts MultiTenant.current_tenant
end

def callback(status, options)
puts "callback"
puts MultiTenant.current_tenant
end
end
```

and the following execution (assuming `1` is a valid tenant ID):

```ruby
MultiTenant.with(1) do
b = Sidekiq::Batch.new
b.on(:success, "TestJob#callback")
b.jobs { TestJob.perform_async }
end
```

You will find that while the tenant is set correctly in `perform`, it is not set in `callback`. This is because of a middleware ordering issue between the multitenant code and the sidekiq-pro batch code.

We were able to work around this issue by manually removing and re-ordering the middleware in our own initializer:

```ruby
# Fix middleware order so that Sidekiq Batch Callbacks are run with a tenant set
chain.remove(Sidekiq::Middleware::MultiTenant::Client)
chain.insert_before(Sidekiq::Batch::Client, Sidekiq::Middleware::MultiTenant::Client)
```

(and the same thing for the server middleware, and the client middleware on the server).

---

Given that this is a sidekiq-builtin feature, it would be nice if this gem could check for the presence of the Batch middleware and insert its middleware in the correct spot by default.