New pot_extrator method to i18n module #17001

Job	Run time
Arch / PyPy	19m 50s
Arch Linux	20m 14s
Ubuntu Rolling (gcc, g++)	20m 12s
CUDA (on Arch)	7m 19s
Ubuntu Rolling (--unity=on -Ddefault_library=static, --no-unittests, gcc, g++)	13m 39s
Fedora	17m 58s
Ubuntu Rolling (-Ddefault_library=both, --no-unittests, gcc, g++)	14m 0s
Gentoo	21m 53s
Ubuntu Rolling (clang, clang++)	22m 13s
OpenSUSE	17m 18s
Ubuntu Rolling (--unity=on, --no-unittests, clang, clang++)	16m 12s
Ubuntu Bionic	14m 18s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, 0, gcc, g++)	13m 47s
Ubuntu Rolling (--cross ubuntu-armhf.json --cross linux-mingw-w64-64bit.json, --unity=on, gcc, g++)	14m 12s
	3h 53m 5s

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