This PR:

1. fixes the devtools_tool update-perfetto command for updates to the perfetto project build system
2. Updates the devtools CSS for the perfetto embedding
3. Updates the perfetto assets to the latest build. The build includes the unlanded change https://android-review.git.corp.google.com/c/platform/external/perfetto/+/3014175 to fix a critical bug.

Please only review the following changes (the remaining changes are from the new Perfetto assets):

1. anything under devtools_app/
2. anything under perfetto_ui_compiled/lib/devtools
3. the update_perfetto.dart tool command

Fixes #7315