[A11y metrics] Add pumpkin and facegaze DLC install metrics

This change adds metrics for:
1. Pumpkin installation duration
2. FaceGaze assets installation duration
3. FaceGaze assets installation success

Bug: b/331400834
Change-Id: I4b1b363942434a52c679f24dd7b56d76e8a422db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5420909


Reviewed-by: Katie Dektar <katie@chromium.org>
Reviewed-by: Evan Liu <evliu@google.com>
Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282604}