SF: Move FrameTimeline into Scheduler

As part of decoupling the FrameTimeline and TokenManager it became
apparent that having FrameTimeline in its own directory didn't make a
lot of sense. Following this, the frametimeline namespace can also be
removed.

Bug: 414584347
Test: none
Flag: EXEMPT, refactor
Change-Id: I6a8d25c3433e78681ed0e1b6025b5441462435e3