[stubtest] Test `NamedTuple` definitions with default fields #10665

Job	Run time
Test mypyc suite with 32-bit Python	14m 20s
Test suite with py38-ubuntu, mypyc-compiled	26m 6s
Test suite with py38-windows-64	35m 24s
Test suite with py39-ubuntu	31m 22s
Test suite with py310-ubuntu	20m 29s
Test suite with py311-ubuntu, mypyc-compiled	18m 34s
Test suite with py312-ubuntu, mypyc-compiled	23m 28s
mypyc runtime tests with py38-macos	7m 2s
mypyc runtime tests with py38-debug-build-ubuntu	6m 39s
Type check our own code (py38-ubuntu)	2m 6s
Type check our own code (py38-windows-64)	4m 30s
Formatting and code style with Black + ruff	46s
	3h 10m 46s

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