Add support for `eigvals`, `svdvals` and `diag`, `diagm`. #236

Job	Run time
Julia 1.6 - ubuntu-latest - x64	17m 7s
Julia 1.6 - macOS-latest - x64	14m 0s
Julia 1.6 - windows-latest - x64	25m 34s
Julia 1 - ubuntu-latest - x64	12m 44s
Julia 1 - macOS-latest - x64	11m 18s
Julia 1 - windows-latest - x64	14m 50s
Julia nightly - ${{ matrix.os }} - ${{ matrix.arch }}	0s
	1h 35m 33s

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