py/vm: Factor cached map lookup code to inline function.
py/vm: Factor cached map lookup code to inline function.

To reduce code duplication and allow to more easily modify this function.

Change-Id: I5c4341471738ade124b6b9082b965bf677b9db10

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython