…r=nical,jrmuizel

This patch removes the old thread_profiler bindings, and adds
support for profiling WR with the tracy profiler, which is a
much more advanced frame profiler.

Since it's very lightweight, and only instruments annotated CPU
and GPU zones, it can retain very large profiles, allowing
fine grained analysis of thread interactions, CPU spikes etc.

Differential Revision: https://phabricator.services.mozilla.com/D66926

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/f8203119cca43d25f2879ebea2b904e4355e59ad