Preload repository cache using MGET

What does this MR do?

This allows us to preload multiple repository cache values using a single MGET command

This fixes a Redis N+1 issue in the projects API

Related to #220329 (closed)

How to setup and validate locally (strongly suggested)

1. Add localhost:3000/api/v4/projects to the performance bar

Notice that the number of Redis calls will be reduced by a lot.

Note that there is another N+1 there for open_issues_count that's going to be fixed by !69479 (merged)

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.