Lums/sc 19401/general node function node cmake cleanup

[lums658]

This PR follows up on lums/sc-19401/general-node-function-node. Its primary additions are

• Clean up of all CMakeLists.txt files under dag and to bring them into compliance with Eric's latest guidance on format and contents. This include definition of some macros to greatly simplify creation of object libraries and unit tests under dag.
• Refine bounded_buffer and add some unit tests for it.
• Refine the documentation for fsm, including proof of correctness for three-stage fsm.
• Include experimental "fxm" for Duff's device based schedulers (this will likely be removed).
• Initial experiments for scheduling, including for Duff's device based schedulers.

---

TYPE: IMPROVEMENT DESC: Clean up CMakeList.txt files under dag.

[shortcut-integration[bot]]

This pull request has been linked to Shortcut Story #19401: General Node (Function Node).