ci: use nextest for faster test execution #286

Job	Run time
Default Features (batteries_included + v4)	22s
Test Suite (v2_public)	58s
Security Audit	2m 44s
Test Suite (v3_local)	1m 0s
Clippy (v1_local)	28s
Test Suite (v2_local)	57s
Clippy (v3_local)	28s
Test Suite (v4_public)	1m 1s
Test Suite (v1_local)	59s
Clippy (v3_public)	26s
Clippy (v2_public)	32s
Test Suite (v4_local)	1m 0s
Test Suite (v3_public)	1m 9s
Clippy (v1_public)	32s
Clippy (v4_local)	30s
Clippy (v4_public)	30s
Test Suite (v1_public)	55s
Clippy (v2_local)	19s
	14m 50s

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