Audit successful GPG keys creation and removal

What does this MR do?

Audit successful GPG key creation and removal via app and API.

How to test

Via App

1. Authenticated to the app as a user, and follow the steps to create and remove GPG Key
2. Create https://docs.gitlab.com/ee/user/project/repository/gpg_signed_commits/#adding-a-gpg-key-to-your-account
3. Remove https://docs.gitlab.com/ee/user/project/repository/gpg_signed_commits/#removing-a-gpg-key

Via API

1. Authenticated to the RESTFul API, and follow the steps to create and remove GPG Key
2. Create https://docs.gitlab.com/ee/api/users.html#add-a-gpg-key
3. Remove https://docs.gitlab.com/ee/api/users.html#delete-ssh-key-for-current-user

Screenshots or Screencasts (strongly suggested)

Navigate to Admin Area > Monitoring > Audit Events and view the newly created audit events

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

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 browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #220127 (closed)