Function to_boundary is not working with preconditioners

[amontoison]

The norm used for the trust-region should be modified if a preconditioner is provided.
We should use the Euclidean norm only when M=I in CG and CR.
https://github.com/JuliaSmoothOptimizers/Krylov.jl/blob/main/src/krylov_utils.jl#L376-L392

Because we can also directly provide estimates of xNorm2 and dNorm2, the final result can be completely wrong because
they are not always computed in Euclidean norm.

cc: @paraynaud
Be careful if you use it with preconditioners.

[paraynaud]

I don't use any preconditioner for now, I'll tell you if I plan to add one in the future 😃