trace_events: destroy platform before tracing

For safer shutdown, we should destroy the platform – and background
threads - before the tracing infrastructure is destroyed. This change
fixes the relative order of NodePlatform disposition and the tracing
agent shutting down. This matches the nesting order for startup.

Make the tracing agent own the tracing controller instead of platform
to match the above.

Fixes: https://github.com/nodejs/node/issues/22865

PR-URL: https://github.com/nodejs/node/pull/22938


Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>