Make Layout/AccessModifierIndentation work with arbitrary blocks

[deivid-rodriguez]

This PR makes the Layout/AccessModifierIndentation cop work for arbitrary blocks, and not only for dynamic class or module definitions. It is built on top of #6573, so any revieweres please have a look at that one first.

This PR changes the expectation of an existing spec, which explicitly stated that this case should not be detected. I don't see why, though. The spec was introduced in d2c0423 as part of a refactor. Neither the commit message nor the associated PR explain the reason for the spec, so I would appreciate some input here.

Also, I'm unsure whether to tag this a "bug fix", "feature", or "change" if this is accepted 😃.

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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 Changed 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 bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[bbatsov]

I messed up a little bit, as I accidentally squashed the commits in your other PR. Rebase to master and I'll merge this one as well.

[deivid-rodriguez]

@bbatsov I rebased it and, although I'm not fully sure about how to tag this PR, I went with calling this a bug fix.

[bbatsov]

Thanks!