Use EnterpriseCompanionStatus for mojom interface

IPC calls should return the canonical status type:
EnterpriseCompanionStatus.

Changing the stable mojom in a backwards-incompatible way here is
permissible as the project has not shipped. Presubmits are disabled
here because there is otherwise no way to supress the
check_stable_mojom_compatibility presubmit.

No-Presubmit: true
Bug: 342180612
Change-Id: Ic055eeb51d71d1f654738863a9dff544ff2f6fe3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5650706
Commit-Queue: Noah Rose Ledesma <noahrose@google.com>
Reviewed-by: Elly FJ <ellyjones@chromium.org>
Reviewed-by: S Ganesh <ganesh@chromium.org>
Reviewed-by: Sorin Jianu <sorin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1320563}