Multizone with species transport

[bigfooted]

Proposed Changes

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

Multizone does not work yet for species transport
This is a WIP to discuss the implementation details online. It does not work yet!

Related Work

Resolve any issues (bug fix or feature request), note any related PRs, or mention interactions with the work of others, if any.
As mentioned in #1818

PR Checklist

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• 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 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]

@EvertBunschoten Thanks! That seemed to work!

[bigfooted]

How well does a restart work in general for multizone? I restart from a converged solution and the result at the zone interface shows high residuals, and I do not recover the exact residual values. The solution looks fine everywhere except at the zone interface. This image below shows the residuals for velocity.
[EDIT: high residuals is relative, it is still 1e-12, but it is higher than what it should be]

[pcarruscag]

What's high in this case? Is it larger than the maximum residuals you have in the rest of the domain?
BTW you need to change the file .github/workflows/regression.yml to point to your testcases branch.