Trace coroutine section name generation

To assess whether coroutine tracing is slow due to context switching,
or if it is slow due to stack unwinding to generate default sections
names, create a new trace section so it can be measured.

Flag: ACONFIG com.android.systemui.coroutine_tracing DISABLED
Bug: 289353932
Test: capture and inspect perfetto trace
Change-Id: I77dcdab40574f1e339c570f6d9984a1bc6aa0644