[owners] Implement ListOwnersForFile for Depot Tools
[owners] Implement ListOwnersForFile for Depot Tools

Add DepotToolsClient to implement the OwnersClient API
for Depot Tools, and implement the ListOwnersForFile method.

Change-Id: I933a262898439d879c919d695aa62d7702b4c9a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2530509
Auto-Submit: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Reviewed-by: Anthony Polito <05bb588aa9020353543fee7ac4e6e0a3d0d6f6ed@google.com>
Commit-Queue: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools