Style/AccessorGrouping: Fix sibling detection for methods with type sigs

[issyl0]

• Over in Homebrew/brew, trying to enable this cop after 008506d was released, we were seeing the following offenses which were incorrect since we can't combine attrs that follow on from typed ones.

  sig { returns(Pathname) }
  attr_reader :cached_location

  attr_reader :cache, :meta, :name, :version
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Group together all `attr_reader` attributes

• This commit ensures that sibling accessors are groupable before raising an offense that they should be grouped.
• Also add more tests to ensure the offense detection and subsequent autocorrection still works.
• Follow up to Style/AccessorGrouping: Fix detection of Sorbet sig {} blocks #11650.

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• 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.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[issyl0]

I ran this (new) test on RuboCop master (v1.48.0) and the autocorrect is completely bugged in the latest release because of the sibling grouping detection. Sorry for not thinking about this sooner! 😳

  1) RuboCop::Cop::Style::AccessorGrouping when EnforcedStyle is grouped registers an offense for grouped accessors distinct from a typechecked accessor method
     Failure/Error: expect(new_source).to eq(correction)
     
       expected: "class Foo\n  extend T::Sig\n\n  sig { returns(Integer) }\n  attr_reader :one\n\n  attr_reader :two, :three, :four\nend\n"
            got: "class Foo\n  extend T::Sig\n\n  sig { returns(Integer) }\n  attr_reader :one\nend\n"
     
       (compared using ==)
     
       Diff:
       @@ -3,7 +3,5 @@
        
          sig { returns(Integer) }
          attr_reader :one
       -
       -  attr_reader :two, :three, :four
        end

[koic]

Thanks!