Tests

[mypyc] Add efficient librt.base64.b64decode #19425

Job	Run time
Test mypyc suite with 32-bit Python	8m 26s
Test suite with py39-ubuntu, mypyc-compiled	15m 8s
Test suite with py313-ubuntu, mypyc-compiled	14m 56s
Test suite with py312-ubuntu, mypyc-compiled	14m 34s
Test suite with py310-ubuntu	12m 24s
Test suite with py311-ubuntu	9m 34s
Test suite with py314-ubuntu, mypyc-compiled	15m 4s
Test suite with py314-windows-64	24m 42s
mypyc runtime tests with py313-macos	5m 30s
mypyc runtime tests with py310-ubuntu	4m 44s
Type check our own code (py39-windows-64)	2m 23s
Type check our own code (py39-ubuntu)	1m 42s
Formatting and code style with Black + ruff	2m 0s
	2h 11m 7s

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