Add `Vec3::slerp` #1504

Job	Run time
Lint	2m 33s
Check MSRV (ubuntu-latest, 1.68.2)	1m 59s
Test (ubuntu-latest, stable)	3m 48s
Check MSRV (macos-latest, 1.68.2)	1m 46s
Test (ubuntu-latest, beta)	3m 23s
Test wasm (stable, ubuntu-latest)	5m 56s
Check MSRV (windows-latest, 1.68.2)	2m 30s
Test (ubuntu-latest, nightly)	3m 11s
Test portable simd (ubuntu-latest, nightly)	46s
Test (macos-latest, stable)	4m 17s
Test portable simd (macos-latest, nightly)	1m 2s
Test (macos-latest, beta)	3m 2s
Test portable simd (windows-latest, nightly)	1m 30s
Test (macos-latest, nightly)	3m 37s
Test (windows-latest, stable)	7m 53s
Test (windows-latest, beta)	6m 6s
Test (windows-latest, nightly)	6m 1s
	59m 20s

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