What should we do with tricky legacy output options? (and other not very useful ones)

[pcarruscag]

Setting WRT_BINARY_RESTART=NO is irrelevant, the output format is determined by OUTPUT_FILES. Is this option around just because of the legacy output? Should it have any effect in the new output?

One needs to set both VISUALIZE_SURFACE_DEF and a surface output format to get a file.
One needs to set both VISUALIZE_VOLUME_DEF and a volume output format to get a file.
Should we just remove these two and let OUTPUT_FILES "decide" what is outputted?

Can we get rid of DISCADJ_LIN_SOLVER and DISCADJ_LIN_PREC and use what is set for the direct solver? Or alternatively, in discrete adjoint problems, use these settings for the primal (recording phase)?
This is annoying because if you use FGMRES for the direct problem and happen to need more linear iterations for the discrete adjoint (say 10 -> 100) in which case you probably switch to BCGSTAB (due to memory), one needs to set/change two options.

If there are options that grind your gears or you think could be more user-friendly lets list them.

[pcarruscag]

Another option mentioned by @talbring is MATH_PROBLEM for which the default could depend on the code being used, i.e. for SU2_CFD_AD and SU2_DOT_AD the default should be DISCRETE_ADJOINT

[pcarruscag]

This is now all covered in #1126