[mypyc] Inline fast paths of integer unboxing operations #12643

Job	Run time
Test mypyc suite with 32-bit Python	7m 45s
Test suite with py38-ubuntu, mypyc-compiled	18m 12s
Test suite with py38-windows-64	20m 13s
Test suite with py39-ubuntu	16m 23s
Test suite with py310-ubuntu	17m 3s
Test suite with py311-ubuntu, mypyc-compiled	16m 12s
Test suite with py312-ubuntu, mypyc-compiled	18m 15s
mypyc runtime tests with py39-macos	6m 5s
mypyc runtime tests with py38-debug-build-ubuntu	4m 29s
Type check our own code (py38-ubuntu)	1m 54s
Type check our own code (py38-windows-64)	2m 26s
Formatting and code style with Black + ruff	44s
	2h 9m 41s

Provide feedback