perfetto: Dynamically create and remove trace event triggers

Using a persistent event trigger for rss_stat_throttled was
found to cause regression of 8% more CPU cycles in kswapd.

Have perfetto dynamically create these triggers when needed
and cleanup the trigger once the perfetto session no longer
needs it.

Triggers are created/removed when the associated trace
event is enabled/disabled by perfetto, so multiple sessions
with the same event trigger are inherently handled correctly
by the same ftrace_config_muxer logic for enabling/disabling
ftrace events.

The persistent rss_stat_throttled histogram trigger will be changed
to an as-needed trigger created by perfetto. So the existence of
this event trigger can no longer be used to check if the kernel
supports throttling rss_stat event.

Instead test creating a histogram trigger with division
arithmetic (needed for event throttling) on rss_stat_throttled.
Creating the trigger on rss_stat_throttled also implicitly checks
that the synthetic throttled event is present.

Test: adb push test/configs/rss_stat.cfg /data/local/tmp/
        && cf-adb shell 'cat /data/local/tmp/rss_stat.cfg |
	   perfetto --txt -c - -o /data/misc/perfetto-traces/trace
Bug: 236172293
Change-Id: I9e14d56bb442129ea85163e492e00382eb8d8994
Merged-In: I9e14d56bb442129ea85163e492e00382eb8d8994
Merged-In: Ifa50c9e08893c8494739747fe77ab1ceec5c0dfd