[SurfaceFlinger] Split VSyncModulator into .cpp/.h files

Future changes require this so that trace events can be added for this
class.

Bug: 133325345
Test: builds
Change-Id: I7b70a9df500b0fca5ae14e2b414d44ca11edf3ce
(cherry picked from commit b488afaa2addf5b101ef24d0e8fc9812cb3c7f26)
Merged-In: I7b70a9df500b0fca5ae14e2b414d44ca11edf3ce
3 files changed