Disable DispSync resync when not needed

If app and SF events aren't using phase offsets, we don't need
to maintain the DispSync model.  We just turn hardware VSYNC on
whenever something wants to draw.  This avoids some edge cases
where we were doing too much resync work.

Also, updated the systrace output.  The "VsyncOn" line was a
combination of SF and app event threads, and would occasionally
be very weird.  Removed VsyncOn, renamed VSYNC to VSYNC-app,
and added VSYNC-sf.

Also, added more details to the --dispsync dumpsys output.

Also, renamed global constants to not look like local variables.

Bug 15516453

Change-Id: I0da10b72f0d9a7b7eb5202d87cc18967f698adbd