Optimise memcpy_nontemporal_sve #1212

Job	Run time
all-builds	2m 9s
coverage	2m 9s
lint	1m 9s
test-cxx (ubuntu-20.04, g++-9)	39s
test-python (ubuntu-20.04, gcc-9, g++-9, 3.9)	1m 15s
test-cxx (ubuntu-22.04, g++-12)	46s
test-python (ubuntu-22.04, gcc-12, g++-12, 3.12)	1m 5s
test-cxx (ubuntu-20.04, clang++-10)	58s
test-python (ubuntu-20.04, clang-10, clang++-10, 3.12)	1m 37s
test-cxx (ubuntu-22.04, clang++-14)	49s
test-python (ubuntu-22.04, clang-14, clang++-14, 3.12)	59s
test-cxx (macos-14, clang++)	1m 13s
test-python (macos-14, clang, clang++, 3.12)	1m 40s
sdist	1s
cibuildwheel-macos	1s
cibuildwheel-linux	1s
combine	1s
	16m 32s

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