feat(platform/azure): check targetBranch when finding PRs (#23941)

lib/modules/platform/azure/__snapshots__/index.spec.ts.snap

lib/modules/platform/azure/index.spec.ts

lib/modules/platform/azure/index.ts

lib/modules/platform/types.ts

lib/workers/repository/cache.ts

lib/workers/repository/config-migration/branch/index.ts

lib/workers/repository/config-migration/pr/index.ts

lib/workers/repository/error-config.ts

lib/workers/repository/finalize/prune.ts

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

lib/workers/repository/onboarding/pr/index.ts

lib/workers/repository/process/limits.ts

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

lib/workers/repository/update/branch/check-existing.ts

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

lib/workers/repository/update/pr/index.ts