SurfaceFlinger: add debug information when vsync is not generated

Print debug information about VsyncReactor internal state when
we expect a vsync event but it is not generated.

Bug: 151892277
Test: adb shell dumpsys SurfaceFlinger --dispsync
Test: simulate a missed vsync and observed logcat
Change-Id: Ia98cb884321d0c25610c4d721f422d9cd05c8c5e