[WIP] multigrid linear prolongation with tigher full multigrid turbulence integration - #2931

Proposed Changes

Give a brief overview of your contribution here in a few sentences.

Implement linear prolongation as alternative to piecewise constant prolongation for multigrid. This allows some cases to use higher damping coefficients for the multigrid smoother and slightly faster convergence..
Furthermore, for full multigrid the fine grid turbulence solver was not being updated, so basically turbulence was frozen during the warmup phase. Now, we update the fine grid turbulence every level change. This leads to slightly better performance for turbulent cases with full multigrid.
There was also a small issue still with the implicit line agglomeration when a wall touches a symmetry that was fixed. It is again a small improvement when implicit line agglomeration is used.

The current implementation is still sensitive to mpi. specifically the way mpi interfaces are constructed by parmetis.

PR Checklist

Put an X by all that apply. You can fill this out after submitting the PR. If you have any questions, don't hesitate to ask! We want to help. These are a guide for you to know what the reviewers will be looking for in your contribution.

• 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.