Prohibit unsupported features on Requirement Issues

This is broken out from #323779 (closed), specifically Stage IIa.

We're moving Requirement objects to Requirement Issues, but we don't want to accidentally introduce new functionality for them. So we need to identify the issue features that Requirements don't have and prohibit them.

This will most likely involve adding to https://gitlab.com/gitlab-org/gitlab/blob/master/ee/app/models/concerns/ee/issue_available_features.rb#L15. Here is an example !50396 (merged).

Features that need to be blocked (further context: #323779 (comment 632031203)):

• moving to another project
• promote to epic
• lock? etc.

Some of these have been done already and may not need doing.

Related to #323779 (closed)