Naming/FileName: Detect constant assignment

[splattael]

Is your feature request related to a problem? Please describe.

Currently, Naming/FileName always flag the following code:

lib/something/bar.rb

module Something
  Bar = Struct.new(:bar)
end

which produces

Offenses:

lib/something/bar.rb:1:1: C: Naming/FileName: bar.rb should define a class or module called Something::Bar.
module Something
^

Describe the solution you'd like

It'd be great to support such constant assignments.

Describe alternatives you've considered

In this example, one could use class Bar < Struct.new(:bar) but those workarounds are not always feasible.

Additional context

See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/73252#note_717026413

[splattael]

We might also want to support aliasing as in:

module Something
  Bar = ::OtherNamespace::Bar
end