add {,t}{a6,arm64}ios machine types #328

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	30m 38s
ci (a6osx, macos-12)	15m 10s
ci (ta6osx, macos-12)	18m 39s
ci (arm64osx, macos-14)	8m 58s
ci (tarm64osx, macos-14)	10m 19s
ci (i3le, ubuntu-22.04)	11m 40s
ci (ti3le, ubuntu-22.04)	14m 35s
ci (a6le, ubuntu-22.04)	9m 0s
ci (ta6le, ubuntu-22.04, CFLAGS+=-std=gnu89)	11m 58s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 20s
ci (i3nt, windows-2022, vs)	11m 43s
ci (ti3nt, windows-2022, vs)	14m 39s
ci (a6nt, windows-2022, vs)	11m 21s
ci (ta6nt, windows-2022, vs)	14m 20s
ci (ta6nt, windows-2022, gcc, CFLAGS+=-std=gnu89)	13m 15s
	3h 24m 35s

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