Offend allow_any_instance_of and expect_any_instance_of in RSpec/SubjectStub

[lovro-bikic]

Expands RSpec/SubjectStub to offend allow_any_instance_of and expect_any_instance_of on the subject (useful in case the subject is a class):

allow_any_instance_of(subject).to receive(:foo)
expect_any_instance_of(subject).to receive(:bar)

---

Before submitting the PR make sure the following are checked:

• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Updated documentation.
• Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

If you have created a new cop:

• Added the new cop to config/default.yml.
• The cop is configured as Enabled: pending in config/default.yml.
• The cop is configured as Enabled: true in .rubocop.yml.
• The cop documents examples of good and bad code.
• The tests assert both that bad code is reported and that good code is not reported.
• Set VersionAdded: "<<next>>" in default/config.yml.

If you have modified an existing cop's configuration options:

• Set VersionChanged: "<<next>>" in config/default.yml.

[pirj]

I can’t recall if I’ve seen such usage ever before. Is this common?

[lovro-bikic]

I've seen it a couple times, but I think this change makes even more sense in conjunction with this one #2088, which is part of the reason why I opened this PR.

allow_any_instance_of(described_class).to receive(:author) is common in my experience.

[pirj]

This is a consequence of usage of the above subject definition.

Do you feel that allow_any_instance_of(Article).to receive(:author).and_return(nil) is wrong, and why?