Separate ARM and ARM SVE tags and add SVE2 detectors #19

Job	Run time
macosx (clang, x86_osx, Debug)	23s
clang (clang, x86, Debug)	2m 9s
macosx (clang, x86_osx, Release)	19s
gcc (gcc, x86, Debug)	1m 53s
clang-cl (Debug)	2m 28s
clang (clang, x86, Release)	1m 51s
macosx (gcc, x86_osx, Debug)	20s
gcc (gcc, x86, Release)	1m 50s
clang-cl (Release)	43s
macosx (gcc, x86_osx, Release)	25s
gcc (gcc, aarch64, -Wno-psabi, Debug)	1m 51s
msvc (Debug)	1m 16s
gcc (gcc, aarch64, -Wno-psabi, Release)	1m 46s
wasm (clang, wasm, Debug)	1m 54s
msvc (Release)	1m 11s
gcc (gcc, aarch64.sve, -Wno-psabi, Debug)	1m 49s
wasm (clang, wasm, Release)	2m 3s
gcc (gcc, aarch64.sve, -Wno-psabi, Release)	1m 46s
gcc (gcc, ppc64, -Wno-psabi, Debug)	1m 45s
gcc (gcc, ppc64, -Wno-psabi, Release)	1m 53s
	29m 35s

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