[mypyc] Promotion to Value Type optimization #13958

Job	Run time
Test mypyc suite with 32-bit Python	7m 44s
Test suite with py38-ubuntu, mypyc-compiled	1m 22s
Test suite with py38-windows-64	20m 36s
Test suite with py39-ubuntu	17m 26s
Test suite with py310-ubuntu	16m 48s
Test suite with py311-ubuntu, mypyc-compiled	1m 0s
Test suite with py312-ubuntu, mypyc-compiled	1m 4s
Test suite with py313-ubuntu, mypyc-compiled	1m 11s
mypyc runtime tests with py39-macos	6m 43s
Type check our own code (py38-ubuntu)	1m 47s
Type check our own code (py38-windows-64)	2m 21s
Formatting and code style with Black + ruff	55s
	1h 18m 57s

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