[clr-interp] Add support for synchronized methods (#120006)

- The general approach is to wrap the method is a try/finally block
  - This is done by appending some IL to the method, and adding an EH clause
  - This required implementing a few abstraction boundaries so that the code/eh clauses could be rewritten within the interpreter
- Synchronized methods also re-use the shadow this pointer logic
- existing IL which is encoded as a RET needs to actually have the semantics of a LEAVE to to the actual return from the method
- We also have a couple of "intrinsic" tokens which the our implementation of CALL now recognizes.

Author: davidwrighton