[Enrollment v2] Add async function result metrics

Adds metrics to track the result--success, failure, timeout--of async
function calls during the CryptAuth v2 Enrollment flow.

Bug: 899080, 936273
Change-Id: Id60e1025e012e04b5bc8d984559a313fa0aedff1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1745366
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Josh Nohle <nohle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686164}
4 files changed