Add `to_angle` method to 2D vectors #1041

Job	Run time
Test wasm (stable, ubuntu-latest)	6m 34s
Lint	23s
Test portable simd (ubuntu-latest, nightly)	55s
Test (ubuntu-latest, stable)	4m 36s
Test portable simd (macos-latest, nightly)	55s
Test (ubuntu-latest, beta)	3m 22s
Test portable simd (windows-latest, nightly)	1m 53s
Test (ubuntu-latest, nightly)	4m 59s
Test (macos-latest, stable)	4m 52s
Test (macos-latest, beta)	6m 20s
Test (macos-latest, nightly)	7m 38s
Test (windows-latest, stable)	6m 43s
Test (windows-latest, beta)	5m 33s
Test (windows-latest, nightly)	5m 38s
	1h 0m 21s

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