Improve IssuableFinder performance

What does this MR do?

When using IssuableFinder all filters are applied before projects filter. Projects filter is applied in the end based on issues that were already filtered. That should improve performance of Gitlab.com as it has a lot of public projects.

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Fixes #25503 (closed)