This adds a simple PyOpOperand based on MlirOpOperand, which can has
properties for the owner op and operation number.
This also adds a PyOpOperandIterator that defines methods for iter
and next so PyOpOperands can be iterated over using the the
MlirOpOperand C API.
Finally, a uses psuedo-container is added to PyValue so the uses can
generically be iterated.
Depends on D139596
It should be possible to get the context from the operand via the forContext method on PyMlirContextRef.