Improve ExtraSpacing Cop

[jfelchner]

A continuation of #5696

This allows for more complex = alignments which previously either caused false positives or autocorrected to the wrong result, or both.

The ultimate result is to be able to give Rubocop something like this:

def batch
  @areas = params[:param].map do
               var_1 = 123_456
               variable_2 = 456_123
           end
  @another = params[:param].map do
               char_1 = begin
                          variable_1_1     = 'a'
                          variable_1_20  = 'b'

                          variable_1_300    = 'c'
                          # A Comment
                          variable_1_4000      = 'd'

                          variable_1_50000     = 'e'
                          puts 'a non-assignment statement without a blank line'
                          some_other_length_variable     = 'f'
                        end
               var_2 = 456_123
             end

  render json: @areas
end

and have it autocorrect it to:

def batch
  @areas   = params[:param].map do
                 var_1      = 123_456
                 variable_2 = 456_123
             end
  @another = params[:param].map do
               char_1 = begin
                          variable_1_1  = 'a'
                          variable_1_20 = 'b'

                          variable_1_300  = 'c'
                          # A Comment
                          variable_1_4000 = 'd'

                          variable_1_50000           = 'e'
                          puts 'a non-assignment statement without a blank line'
                          some_other_length_variable = 'f'
                        end
               var_2  = 456_123
             end

  render json: @areas
end

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.
• Run rake default or rake parallel. It executes all tests and RuboCop for itself, and generates the documentation.

[bbatsov]

The changes look reasonable to me, but I'll leave it to @jonas054 to decide whether to accept them.

[jonas054]

I only had one comment. Fix that and we should be ready to merge. 👍

[jfelchner]

@jonas054 rebased!

[bbatsov]

🚀

[jfelchner]

@jonas054 thanks for helping me get this over the line! 1.5 years in the making! 😂

[jonas054]

@jfelchner No problem, I had fun pairing!