ordering of option declarations should not prohibit forward reference in default procs

## Describe the bug

the :default keyword supports an "instance_exec" type of evaluation whereby `default: -> { foo + bar }' reference the object in questions' `foo` and ` bar` methods. however, when either `foo` or `bar` are, themselves, dry-initialized attributes, the default value will resolve to `nil` due to being referenced prior to 'dry initialization'

## To Reproduce

```ruby
require 'dry-initializer'

class A
extend Dry::Initializer
option :foo, default: -> { bar }
option :bar, default: -> { 42 }
end.new

class B
extend Dry::Initializer
option :bar, default: -> { 42 }
option :foo, default: -> { bar }
end.new

pp A.new #=> #
pp B.new #=> #

```

## Expected behavior

@bar == @foo == 42

## My environment

n/a