Update ScopedPerfEventHelper class to add systrace markers by default.
This change unifies ANGLE EVENT* macro system so that at the base level
in LoggingAnnotator class, systrace markers will be added by default.

Modify the base DebugLogger to use char* by default and move any
conversions to wchar_t to the Windows specializations where wchar is
used. This limits type conversions to only where they're needed.

This change also includes some new TRACE_EVENT() calls in the VK
backend which will result in systrace markers for those calls on the
Android platform.

The new build flag "angle_enable_trace" is added to enable the tracing
calls.

Bug: angleproject:2528
Change-Id: Icefc197d4407e1cd31338710e37865abae6a0b15
Reviewed-on: https://chromium-review.googlesource.com/c/1042785
Commit-Queue: Tobin Ehlis <tobine@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>