Cache newly committed branches in branch switcher

What does this MR do?

For #331105 (closed). Dependent on !62871 (merged).

When the user creates a new branch through a commit in the pipeline editor, that new branch will be added to the apollo cache so that it will show up in the branch switcher.

The branch switcher has two queries: one for searching all branches, and one of searching branches with a searchPattern. The latter already uses a network-only fetch policy since it would be difficult to update the cache for each search query where the new branch fits the searchPattern.

This feature sits behind a feature flag , to enable it run:

echo "Feature.enable(:pipeline_editor_branch_switcher)" | rails c

Screenshots

Cache New Branch

Persist Changes When Switching Branches

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?) /database_review.html#required), 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.

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.)