Updates to FSM and Pipeline abstractions and documentation

Description & Motivation

Renamed StateMachine to FiniteStateMachine (deprecated StateMachine name)
Expose mapping from StateIdentifier to state index in FiniteStateMachine
Deprecated clk on Pipeline and FiniteStateMachine abstractions
Allow FiniteStateMachine states to use "priority" (and "none") instead of only "unique".
Add support for multi-trigger support for the Sequentials in FiniteStateMachine and Pipeline abstractions
Refactor the "traffic light FSM" to use newer features from Dart and FiniteStateMachine to be more readable as a helpful example
Update the FSM documentation in the user guide to be more helpful

Fix #409 Fix #372 Fix #406 Fix #400

Modified some tests to cover functionality added

Is this a breaking change that will not be backwards-compatible? If yes, how so?

Some deprecations, but no backwards compatibility breaking changes

Does the change require any updates to documentation? If so, where? Are they included?

Updated some docs and API docs