Infer generic type arguments for slice expressions (#18160) #13933

Job	Run time
Test suite with py38-ubuntu, mypyc-compiled	18m 13s
Test suite with py38-windows-64	20m 28s
Test suite with py39-ubuntu	17m 37s
Test suite with py310-ubuntu	16m 34s
Test suite with py311-ubuntu, mypyc-compiled	16m 3s
Test suite with py312-ubuntu, mypyc-compiled	18m 15s
Test mypyc suite with 32-bit Python	7m 3s
Test suite with py313-ubuntu, mypyc-compiled	18m 45s
mypyc runtime tests with py39-macos	5m 47s
Type check our own code (py38-ubuntu)	1m 50s
Type check our own code (py38-windows-64)	2m 9s
Formatting and code style with Black + ruff	56s
	2h 23m 40s

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