Track changes in merge request approval settings in Audit Events

What does this MR do?

Closes #336211 (closed).

This MR brings new project's Audit Events related to MR Approval settings. As it was first introduced in #7531 (closed) and then in #209222 (closed), we need to track all changes in project Settings > General > Merge request (MR) approvals > Approval Settings (some of them are new and not tracked).

Screenshots

Recorded Audit Events:

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers
• I have added/updated documentation
• I have properly separated EE content from FOSS
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance.
• This change is backwards compatible across updates

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browser.

Security

N/A