Add Armv7M support for Cortex-M4 and Cortex-M7 #435

Job	Run time
examples_basic	39s
Dry Run (slothy.targets.arm_v7m.cortex_m4)	1m 37s
examples_ntt_kyber_dilithium_neon_core	23m 42s
examples_ntt_kyber_dilithium_helium_core	2m 44s
fft	6m 24s
Dry Run (slothy.targets.arm_v7m.cortex_m7)	25m 44s
sqmag	1m 1s
Dry Run (slothy.targets.arm_v81m.cortex_m55r1)	3m 20s
tutorial	13m 8s
Dry Run (slothy.targets.arm_v81m.cortex_m85r1)	2m 13s
Dry Run (slothy.targets.aarch64.cortex_a55)	9m 33s
Dry Run (slothy.targets.aarch64.cortex_a72_frontend)	38m 13s
Dry Run (slothy.targets.aarch64.apple_m1_firestorm_experimental)	27m 43s
Dry Run (slothy.targets.aarch64.apple_m1_icestorm_experimental)	24m 16s
	3h 0m 17s

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