The client API provides a much simpler interface so that we don't have
to deal with producers, consumers etc. directly. This CL removes all the
code that dealt with the more complex API used previously.

The architecture used here requires that the embedder call into
Tracing::Initialize() to set up the tracing backend. The tracing
controller then connects to this backend when calling
DataSource::Register() and Tracing::NewTrace(). This will ultimately
avoid the need for a virtual call (or two) for every trace event that
need to be dispatched over the API - chrome can provide a backend
and V8 will connect to it opaquely with the same code when tracing is
enabled.

Cq-Include-Trybots: luci.v8.try:v8_linux64_perfetto_dbg_ng
Bug: v8:8339
Change-Id: I6b74fbb49ffcc89638caeb59ed3d5cc81238f3e8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1634916Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62568}