Tests

Use u8 for type/symbol tags #17718

Job	Run time
Test mypyc suite with 32-bit Python	9m 29s
Test suite with py39-ubuntu, mypyc-compiled	28m 48s
Test suite with py310-ubuntu	10m 32s
Test suite with py312-ubuntu, mypyc-compiled	15m 20s
Test suite with py311-ubuntu	9m 9s
Test suite with py314-dev-ubuntu	26m 20s
mypyc runtime tests with py39-macos	6m 51s
Test suite with py313-windows-64	22m 43s
Type check our own code (py39-windows-64)	2m 45s
Test suite with py313-ubuntu, mypyc-compiled	19m 41s
Type check our own code (py39-ubuntu)	1m 46s
Formatting and code style with Black + ruff	1m 48s
	2h 35m 12s

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