Add Armv7M support for Cortex-M4 and Cortex-M7 #526

Job	Run time
examples_ntt_kyber_dilithium_neon_core	17m 7s
examples_ntt_kyber_dilithium_helium_core	3m 13s
examples_basic	1m 28s
Dry Run (slothy.targets.arm_v7m.cortex_m4)	1m 33s
fft	7m 17s
Dry Run (slothy.targets.arm_v7m.cortex_m7)	33m 5s
sqmag	1m 42s
tutorial	6m 26s
Dry Run (slothy.targets.arm_v81m.cortex_m55r1)	3m 37s
Dry Run (slothy.targets.arm_v81m.cortex_m85r1)	2m 22s
Dry Run (slothy.targets.aarch64.cortex_a55)	7m 53s
Dry Run (slothy.targets.aarch64.cortex_a72_frontend)	30m 44s
Dry Run (slothy.targets.aarch64.apple_m1_firestorm_experimental)	25m 13s
Dry Run (slothy.targets.aarch64.apple_m1_icestorm_experimental)	23m 21s
	2h 45m 1s

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