Benchmark `Trace.cpp:SuppressionMap`

[xis19]

Trace.cpp:SuppressionMap would (1) create a copy of the TraceEvent type string (2) Store the string inside the std::map data structure.

Considering the frequency of using TraceEvent it might be interesting to see:

1. It is possible that SuppressionMap will only create a copy of the TraceEvent::type when it is unknown.
2. Try std::unordered_map or some other custom implementation?