[Files TS] Convert volume_manager_util and unit test to TS

* Merge volume_manager_util into volume_manager_impl.ts because
  that's the only file which uses volume_manager_util.
* Update definition build rule for test_build_ts because we also
  need those types in unit tests files (e.g. chrome.runtime)
* Make VolumeInfoImpl accepts null FileSystem.

Bug: b:289003444
Test: browser_tests --gtest_filter="*.VolumeManagerTest"
Change-Id: Ie31e28ad9957b19a519ebe879b2b249af1573beb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5003807
Commit-Queue: Wenbo Jie <wenbojie@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1220712}