Update mlpcpp

[EvertBunschoten]

Proposed Changes

Major update to the MLPCpp submodule aimed at improving network inference efficiency, flexibility of the various classes within the submodule, and paving the way to enabling physics-informed machine learning in SU2.

The CDataDrivenFluid and CFluidFlamelet classes required adaptation to exploit the new capabilities, reducing the computational cost of data-driven fluid simulations.

Furthermore, a new unit test was added that checks differentiation of the network inference function and compares the Jacobian and Hessian of the network output to the analytical values calculated with MLPCpp.

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.