Pass mutable copies to inplace LinearAlgebra functions (#52504)
This gets some functions working with immutable matrix types, e.g.:
```julia
julia> using FillArrays, LinearAlgebra
julia> F = Fill(big(2), 4, 4)
4×4 Fill{BigInt}, with entries equal to 2
julia> det(F)
0
julia> triu(F)
4×4 Matrix{BigInt}:
2 2 2 2
0 2 2 2
0 0 2 2
0 0 0 2
```
