[WIP] Addition of SLAU, SLAU2, and AUSM+-Up Schemes to NEMO

[WallyMaier]

Proposed Changes

This adds more AUSM family schemes.

Related Work

This is a continuation of PR #1773

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.

• [x] I am submitting my contribution to the develop branch.
• [ ] My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• [x] My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• [ ] 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.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If this is still a relevant issue please comment on it to restart the discussion. Thank you for your contributions.