Refine selftest further #483

Job	Run time
examples_ntt_kyber_dilithium_helium_core	2m 45s
Dry Run (slothy.targets.arm_v7m.cortex_m7)	40s
examples_basic	42s
Dry Run (slothy.targets.arm_v81m.cortex_m55r1)	3m 17s
examples_ntt_kyber_dilithium_neon_core	6m 50s
Dry Run (slothy.targets.arm_v81m.cortex_m85r1)	2m 11s
fft	6m 30s
Dry Run (slothy.targets.aarch64.cortex_a55)	9m 5s
tutorial	14m 44s
sqmag	57s
Dry Run (slothy.targets.aarch64.cortex_a72_frontend)	37m 3s
Dry Run (slothy.targets.aarch64.apple_m1_firestorm_experimental)	26m 31s
Dry Run (slothy.targets.aarch64.apple_m1_icestorm_experimental)	23m 34s
	2h 14m 49s

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