Category isn't preserved by timeline events as `Dart_TimelineEvent`
specifies the category as `embedder`.

Fixes: https://github.com/flutter/flutter/issues/60008

As of flutter.dev/go/engine-cpu-profiling, we collect the CPU and
Memory usage. With work being done to collect GPU usage on iOS as well.

This adds them to the timeline summary.

Fixes: https://github.com/flutter/flutter/issues/58803