Allow Procs inside the `Configuration.allowed_deprecations` array:

[Edouard-chin]

• It's sometimes useful to allow some deprecations based on where they get called from.

  Imagine this kind of code:

  def foo
    1000.times do
      deprecation_call
    end
  end
  
  def bar
    deprecation_call
  end
  
  private
  
  def deprecation_call
    ActiveSupport::Deprecation.warn('Something')
  end

  Calling foo, will trigger a thousand deprecations that you'll to record. You currently can whitelist the Something deprecation, but if you do that will also ignore the deprecation that gets triggered when calling bar.

  If you want to fine grain, which deprecations should be allowed based on the caller, then this PR allows you that.

  The Configuration.allowed_deprecations now accepts procs. Procs will be passed the deprecation message as well as the stacktrace. Your proc needs to return a truthy value if the deprecation is allowed.