[trace] rename ThreadIntelPT into TraceTrace

Renamed ThreadIntelPT to TreaceThread, making it a top-level class. I noticed that this class can and shuld work for any trace plugin and there's nothing intel-pt specific in it.
With that TraceThread change, I was able to move most of the json file parsing logic to the base class TraceSessionFileParser, which makes adding new plug-ins easier.

This originally was part of https://reviews.llvm.org/D89283

Differential Revision: https://reviews.llvm.org/D89408