Add `to_angle` method to 2D vectors #1043

Job	Run time
Lint	3m 24s
Test portable simd (ubuntu-latest, nightly)	1m 12s
Test wasm (stable, ubuntu-latest)	5m 23s
Test portable simd (macos-latest, nightly)	1m 47s
Test (ubuntu-latest, stable)	4m 1s
Test portable simd (windows-latest, nightly)	2m 10s
Test (ubuntu-latest, beta)	3m 15s
Test (ubuntu-latest, nightly)	4m 5s
Test (macos-latest, stable)	6m 2s
Test (macos-latest, beta)	6m 19s
Test (macos-latest, nightly)	3m 50s
Test (windows-latest, stable)	6m 55s
Test (windows-latest, beta)	7m 51s
Test (windows-latest, nightly)	5m 14s
	1h 1m 28s

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