Add the excessive_create_list FactoryBot cop

[ddieulivol]

Cop used to signal when we create a lot of factory objects with FactoryBot (configurable with the MaxAmount option).

        # @example MaxAmount: 10 (default)
        #   # We do not allow more than 10 items to be created
        #
        #   # bad
        #   create_list(:merge_request, 1000, state: :opened)
        #
        #   # good
        #   create_list(:merge_request, 10, state: :opened)
        #

---

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]

Thank you, the cop looks good.
I’ve added notes, mostly minor and cosmetic.

We’ve moversxtracted all FB cops to https://github.com/rubocop/rubocop-factory_bot/tree/master/lib/rubocop/cop/factory_bot
Please retarget the PR there.

[pirj]

The failing spec tells that you have to add yourself in the bottom of the changelist, alphabetically.

[pirj]

This should go to https://github.com/rubocop/rubocop-factory_bot

[ddieulivol]

This should go to https://github.com/rubocop/rubocop-factory_bot

New MR is at rubocop/rubocop-factory_bot#83