feat(QuantumMechanics): Add orthogonal subspaces

[gloges]

Adds several orthogonal subspaces for unbounded operators:

• HasDenseDomain.orthogonal_range : U.rangeᗮ = U†.ker
• HasDenseDomain.orthogonal_adjoint_ker : U†.kerᗮ = U.range.closure
• IsUnbounded.orthogonal_adjoint_range : U†.rangeᗮ = U.closure.ker
• IsUnbounded.orthogonal_closure_ker : U.closure.kerᗮ = U†.range

Also two variants useful for the spectral theory (the latter holds for z in the regularity domain):

• IsUnbounded.orthogonal_closure_sub_range : (T.closure - z • 1).rangeᗮ = (T† - conj z • 1).ker
• IsUnbounded.orthogonal_adjoint_sub_ker : (T† - conj z • 1).kerᗮ = (T.closure - z • 1).range

[gloges]

t-quantum-mechanics

[github-actions]

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[jstoobysmith]

This all looks good to me! Approved. Many thanks.