Open PRs against LinearAlgebra in julia repo

[KristofferC]

These are PRs that:

1. Have the linear algebra label
2. Only modify files in stdlib/LinearAlgebra

PR #56611: Update svd.jl documentation
PR #56506: use LQ for "wide A" \ b, not QR
PR #56500: Fixed opnorm
PR #56439: [LinearAlgebra] Use BLAS.trsm! instead of LAPACK.trtrs! in generic_trimatdiv!
PR #56397: Inline `wrap` in triangular `generic_matmatmul`
PR #56362: Narrower `MulAddMul` stabilization in bidiag `mul!`
PR #56259: LinearAlgebra support for cross product of 3-tuples
PR #56170: Add a convenience constructor for `MulAddMul`
PR #56013: 2-arg `show` for `Symmetric`/`Hermitian` and triangular
PR #55830: Make output type promotion for `LinearAlgebra.normalize` GPU friendly
PR #55821: Use matprod_dest in triangular multiplications
PR #55630: Infer eltype from diag element in off-diag bands for structured matrices
PR #55604: Unwrap parent in triangular broadcast
PR #55481: LinearAlgebra: move alg to a keyword argument in symmetric eigen
PR #55431: Handle large integer exponents in matrix powers
PR #55169: `propertynames` for SVD respects private argument
PR #54997: Add a "lower" `cat` method for LinearAlgebra types
PR #54723: Map instead of broadcast in Diagonal matrix functions
PR #54440: Let `diagzero` propagate information not stored in type where relevant
PR #54190: Fix size-1 `StructuredMatrix`'s broadcast.
PR #53449: zero(::ArrayWrapper) forwards to parent
PR #52805: Type-stabilize generic matrix solves
PR #52787: Promote more BLAS-able cases to BLAS methods
PR #51245: Respect pivot strategy (if given) in `cholesky`
PR #50955: Deprecate implicit pseudo-inverses of vectors
PR #50621: Rework broadcast for `Adjoint`/`Transpose` of vectors
PR #50423: `getindex` for block `Tridiagonal` matrices
PR #50407: Fill diagonals for structured block matrices using `diagzero`
PR #50092: RFC: Introduce abstract type `AbstractBandedMatrix`
PR #49487: use power iteration for opnorm2
PR #48861: LinearAlgebra traited matrix operations
PR #48657: LinearAlgebra: extend `eigen` with left eigenvectors and errorbounds
PR #44113: Add rcond to LinearAlgebra
PR #43818: Allow modifying off-diagonals of SymTridiagonal
PR #43719: un-revert "Simplify some views of Adjoint matrices"
PR #43552: Allow offset indices in some linear algebra
PR #43459: RFC: Add `norm(A, p; dims)`
PR #43256: faster and simpler generic_norm2
PR #41830: [WIP] enhancement of Eigen API (revision of #38483)
PR #41420: eigensolvers for Hessenberg matrices
PR #41228: fix some issues with equality of factorizations
PR #40769: Make `dot` handle `missing`s
PR #40758: [Do not Merge] Remove implicit pinvs of vectors
PR #38372: Let `cond` of an empty matrix return zero
PR #36862: speedup norm on AbstractArray{<:Number}
PR #34728: Explain boundry cases for set_num_threads
PR #33072: RFC: Refactor LinearAlgebra to use `isa` instead of method dispatch to avoid ambiguity hell
PR #32555: Optimize tridiagonal matrix solver
PR #30138: Structured opnorm
PR #29724: Adding specialized ≈ and norm for structured matrices.