Use Classical Gram–Schmidt twice instead of Modified G-S with conditional re-orthogonalization.

[pcarruscag]

Proposed Changes

Doing CGS twice is faster (if not implemented naively) and at least as robust.

• other small linear algebra improvements.

PR Checklist

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• I used the pre-commit hook to prevent dirty commits and used pre-commit run --all to format old commits.
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary.

[bigfooted]

Nice! So it's faster per iteration, not faster because it converges in less iterations I guess? How much faster re we talking about?

[pcarruscag]

Yes per iteration. Maybe 1.4x for the orthogonalization part, which is only significant for many linear iterations since it scales quadratically.
So this is mostly for Adjoints with GMRES and FEA/Heat problems.