ci: split out `multiprocess` linting to a separate step on Actions #335

Job	Run time
Build container / Build container	23s
Build slim container / Build container	30s
x86_64-pc-linux-gnu / Build depends	1m 2s
x86_64-pc-linux-gnu_multiprocess / Build depends	55s
arm-linux-gnueabihf / Build depends	1m 3s
x86_64-pc-linux-gnu_nowallet / Build depends	53s
x86_64-apple-darwin / Build depends	1m 1s
x86_64-w64-mingw32 / Build depends	55s
linux64_nowallet-build / Build source	6m 27s
win64-build / Build source	10m 9s
linux64_tsan-build / Build source	11m 13s
linux64_multiprocess-build / Build source	36m 25s
mac-build / Build source	3m 34s
linux64-build / Build source	5m 53s
linux64_fuzz-build / Build source	17m 26s
linux64_ubsan-build / Build source	6m 47s
linux64_sqlite-build / Build source	6m 13s
arm-linux-build / Build source	3m 50s
linux64-test / Test source	34m 35s
linux64_sqlite-test / Test source	29m 33s
linux64_nowallet-test / Test source	13m 11s
linux64_ubsan-test / Test source	33m 35s
linux64_tsan-test / Test source	49m 47s
linux64_multiprocess-test / Test source	48m 38s
	5h 23m 58s

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