Summary:
## Changelog:
[Internal] - Add unit tests for the WebPerformance library (PerformanceEntryReporter)
This sets up a C++ unit test suite for `PerformanceEntryReporter` (the core part of the native side of WebPerformance) and adds test coverage for its core functionality.
Reviewed By: sammy-SC
Differential Revision: D43771370
fbshipit-source-id: ad3e0f3f206701c2ea6a5c9386458a76699e7c80
Ruslan Shestopalyuk