arc/tracing: perceived FPS metric

Add two perceived event bands and remove the ChromeOS FPS band, as
proposed in http://doc/1NIpVxCLYO4n3wfUHt5GsNwqRpvLkooW0JE2poVrJRg4.

Change the FPS histogram from ChromeOS to perceived, and the summary
stat box from ChromeOS FPS to Perceived FPS.

Sample results in web UI: https://screenshot.googleplex.com/6yazrFjJaAq7nDR.png

Test: ArcGraphicsTracingHandlerTest
Test: trace 32 FPS app on brya DUT
Test: when tracing one app with intermittent animation, and allowing a video to play in a Chrome browser, verify ChromeOS swaps are regular but perceived swaps are intermittent.
Bug: b/296595454
Change-Id: I8d65c69fe67e9b3c91442983fec980d43a2811d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4935109
Commit-Queue: Matthew DeVore <matvore@chromium.org>
Reviewed-by: Alan Ding <alanding@chromium.org>
Reviewed-by: Yury Khmel <khmel@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1211183}