fix: unpack unions inside tuples in except handlers #13150

Job	Run time
Test suite with Python nightly	14m 9s
Test mypyc suite with 32-bit Python	7m 9s
Test suite with py38-ubuntu, mypyc-compiled	17m 37s
Test suite with py38-windows-64	20m 26s
Test suite with py39-ubuntu	19m 36s
Test suite with py310-ubuntu	15m 36s
Test suite with py311-ubuntu, mypyc-compiled	16m 26s
Test suite with py312-ubuntu, mypyc-compiled	18m 43s
mypyc runtime tests with py39-macos	5m 46s
mypyc runtime tests with py38-debug-build-ubuntu	4m 22s
Type check our own code (py38-ubuntu)	1m 52s
Type check our own code (py38-windows-64)	2m 20s
Formatting and code style with Black + ruff	34s
	2h 24m 36s

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