Re-land [Support] Extend TimeProfiler to support multiple threads

This makes TimeTraceProfilerInstance thread local. Added
timeTraceProfilerFinishThread() which moves the thread local instance to
a global vector of instances. timeTraceProfilerWrite() then writes
recorded data from all instances.

Threads are identified based on their thread ids. Totals are reported
with artificial thread ids higher than the real ones.

This fixes the previous version to work with __thread as well as
thread_local.

Differential Revision: https://reviews.llvm.org/D71059