Add AllowMethodComparison option for Lint/MultipleComparison

[koic]

Follow #8939 (comment).

This PR adds AllowMethodComparison option for Lint/MultipleComparison.

# @example AllowMethodComparison: true (default)
#   # good
#   foo if a == b.lightweight || a == b.heavyweight
#
# @example AllowMethodComparison: false
#   # bad
#   foo if a == b.lightweight || a == b.heavyweight
#
#   # good
#   foo if [b.lightweight, b.heavyweight].include?(a)

---

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

[bbatsov]

That's exactly what I had in mind! Thanks!