Tests

[mypyc] Add primitives for librt.strings.StringWriter (#20624) #20291

Job	Run time
Test mypyc suite with 32-bit Python	9m 42s
Test suite with py314t-ubuntu, mypyc-compiled	16m 59s
Test suite with py313-ubuntu, mypyc-compiled	14m 29s
Test suite with py314-ubuntu, mypyc-compiled	15m 20s
Test suite with py310-ubuntu, mypyc-compiled	14m 23s
Test suite with py314-windows-64	27m 13s
Test suite with py312-ubuntu	9m 56s
mypyc runtime tests with py313-macos	6m 6s
mypyc runtime tests with py310-ubuntu	5m 25s
Parallel tests with py314-ubuntu, mypyc-compiled	28m 34s
Parallel tests with py314-ubuntu, interpreted	23m 23s
Type check our own code (py310-ubuntu)	1m 42s
Type check our own code (py310-windows-64)	2m 39s
Test suite with py311-ubuntu	9m 39s
Formatting and code style with Black + ruff	1m 53s
	3h 7m 23s

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