dillon1000/react

Improve tests for 'schedule' module (#12880)

**what is the change?:**
Renamed some methods, and made a method to advance a frame in the test
environment.

**why make this change?:**
We often need to simulate a frame passing with some amount of idle time
or lack of idle time, and the new method makes it easier to write that
out.

**test plan:**
Run the updated tests.
Also temporarily tried breaking the scheduler and verified that the
tests will fail.

**issue:**
See internal task T29442940