Add query-logic to the [MotionSpec] #MotionMechanics

Adding logic to the spec to query breakpoints and segments. This is going to be used in the next CL, in the [MotionValue] implementation.

Background on design and motivation in go/motionvalue-design

Flag: NONE Initial commits for new library, currently unused.
Test: atest mechanics_tests
Bug: 379248269
Change-Id: Ie03fa9fec0c8e9bb88e1e8e27c81ae1b1cb28ea9
7 files changed