[mypyc] Promotion to Value Type optimization #13966

Job	Run time
Test mypyc suite with 32-bit Python	7m 7s
Test suite with py38-ubuntu, mypyc-compiled	17m 59s
Test suite with py38-windows-64	20m 42s
Test suite with py39-ubuntu	17m 20s
Test suite with py310-ubuntu	16m 40s
Test suite with py311-ubuntu, mypyc-compiled	16m 5s
Test suite with py312-ubuntu, mypyc-compiled	18m 20s
Test suite with py313-ubuntu, mypyc-compiled	18m 36s
mypyc runtime tests with py39-macos	4m 23s
Type check our own code (py38-ubuntu)	1m 53s
Type check our own code (py38-windows-64)	2m 28s
Formatting and code style with Black + ruff	1m 13s
	2h 22m 46s

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