feat: improve branch cache logic (#17848)

lib/util/cache/repository/types.ts

lib/util/git/behind-base-branch-cache.spec.ts

lib/util/git/behind-base-branch-cache.ts

lib/util/git/index.spec.ts

lib/util/git/index.ts

lib/util/git/modified-cache.spec.ts

lib/util/git/modified-cache.ts

lib/util/git/set-branch-commit.spec.ts

lib/util/git/set-branch-commit.ts

lib/workers/repository/cache.ts

lib/workers/repository/onboarding/branch/rebase.ts

lib/workers/repository/process/write.spec.ts

lib/workers/repository/process/write.ts

lib/workers/repository/update/branch/reuse.ts