Add traceAsync to TraceUtils

This utility is useful to trace coroutine code, as the beginning and the
end of the event might end up in different threads.

Note that stacks are maintained as long as the same trackName is used.

When no stackName is used, "AsyncTraces" default is used.

Test: New track appearing in a perfetto trace
Bug: 289353932
Change-Id: I0fbf745d058e6a329d6b2229178a52af21e84033