Add GitHub annotations format for `--output` #13177

Job	Run time
Test mypyc suite with 32-bit Python	7m 17s
Test suite with Python nightly	14m 17s
Test suite with py38-ubuntu, mypyc-compiled	17m 50s
Test suite with py38-windows-64	20m 5s
Test suite with py39-ubuntu	19m 20s
Test suite with py310-ubuntu	15m 50s
Test suite with py311-ubuntu, mypyc-compiled	16m 46s
Test suite with py312-ubuntu, mypyc-compiled	18m 2s
mypyc runtime tests with py39-macos	5m 32s
mypyc runtime tests with py38-debug-build-ubuntu	4m 23s
Type check our own code (py38-ubuntu)	2m 1s
Type check our own code (py38-windows-64)	2m 28s
Formatting and code style with Black + ruff	37s
	2h 24m 28s

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