[usb][ums] Refactor UMS integration tests and fix race conditions

- Refactor 'ums-test.cc' to use 'device_watcher' for robust device
  detection and removal.
- Update 'ums-function' driver to track in-flight requests and
  properly handle USB Reset control requests.
- Re-enable the UMS integration test in the Build system.
- Fix argument parsing in 'blktest' to correctly handle '-d' flag.
- Modernize test manifest to use Driver Test Realm.

Depends-on: fuchsia:Ic23b823e38e4d297e1e6ebd25cbea6627b3c1d51
Test: fx test ums-integration-test
Fixed: 317154044
Change-Id: I692c35e2052dca4bebde0ef665c82187b265c284
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1558080
Reviewed-by: HanBin Yoon <hanbinyoon@google.com>
Fuchsia-Auto-Submit: Puneetha Ramachandra <puneetha@google.com>
Dependencies-Satisfied: CL Deps Checker <cl-deps-checker@fuchsia-internal-service-accts.iam.gserviceaccount.com>
Commit-Queue: Puneetha Ramachandra <puneetha@google.com>