Tests

Re-introduce GC freeze hack into parallel checking (#21302) #21904

Job	Run time
Test mypyc suite with 32-bit Python	11m 13s
Test suite with py310-ubuntu, mypyc-compiled	16m 28s
Test suite with py314-ubuntu, mypyc-compiled	15m 20s
Test suite with py312-ubuntu	9m 53s
mypyc runtime tests with py313-macos	7m 5s
Test suite with py314t-ubuntu, mypyc-compiled	18m 8s
Parallel tests with py314-ubuntu, interpreted	24m 35s
Test suite with py311-ubuntu	9m 6s
Test suite with py313-ubuntu, mypyc-compiled	15m 34s
mypyc runtime tests with py310-ubuntu	6m 31s
Parallel tests with py314-ubuntu, mypyc-compiled	30m 32s
Type check our own code (py310-ubuntu)	1m 9s
Parallel tests with py314-windows-64, interpreted	10m 24s
Type check our own code (py310-windows-64)	2m 2s
Test suite with py314-windows-64	30m 52s
Formatting and code style with Black + ruff	1m 50s
	3h 30m 42s

Provide feedback