feat(QuantumMechanics): adjoint of continuous operators

[gloges]

• Adds adjoint_domain_of_continuous: U†.domain = ⊤ when U is a continuous (equivalently, bounded) operator
• Adds HasDenseDomain.adjoint_add_continuous (and a sub variant): (T₁ + T₂)† = T₁† + T₂† with T₂ continuous (equivalently, bounded).
• Simplifies the proof IsUnbounded.orthogonal_closure_sub_range using adjoint_sub_continuous

Also takes the opportunity to move the IsUnbounded section of Unbounded.lean before those for IsSymmetric, etc. so that results for general unbounded operators can be used in more specialized cases.

Currently a draft since will need to merge after #1432.

[github-actions]

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