[mypyc] Promotion to Value Type optimization #13959

Job	Run time
Test mypyc suite with 32-bit Python	7m 8s
Test suite with py38-ubuntu, mypyc-compiled	2m 15s
Test suite with py38-windows-64	20m 38s
Test suite with py39-ubuntu	19m 20s
Test suite with py310-ubuntu	16m 39s
Test suite with py311-ubuntu, mypyc-compiled	1m 37s
Test suite with py312-ubuntu, mypyc-compiled	1m 39s
Test suite with py313-ubuntu, mypyc-compiled	1m 54s
mypyc runtime tests with py39-macos	4m 22s
Type check our own code (py38-ubuntu)	2m 3s
Type check our own code (py38-windows-64)	2m 25s
Formatting and code style with Black + ruff	56s
	1h 20m 56s

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