Iterate both heat and FEA solvers for thermoelastic simulations

[pcarruscag]

Proposed Changes

Iterating the heat solver just once is not enough. Even with a structured mesh and high CFL the heat flux is not correct.
Iterating the two solvers is also necessary to make it fully nonlinear by updating the coordinates used by the heat solver.

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.