Add tests for VsyncSchedule

Follow-on to I54a1304a3428968134cc707b24d5b325927c31df. This is somewhat
covered by existing unit tests, but add more thorough tests just for
VsyncSchedule.

Include thread_annotations.h to fix build.

Update MockSchedulerCallback to include the new interface header.

Bug: 241286146
Test: this
Change-Id: I79e14d67fea896752f0afaba00adc6d47efc3c71
Merged-In: I79e14d67fea896752f0afaba00adc6d47efc3c71