Squashed commit of the following:

commit c0992ea
Author: GeorgiaActon <[email protected]>
Date:   Thu Sep 26 10:55:29 2024 +0100

    Clean up stella: kxky grids, namelists, debug flags, including full_flux_surface automatic numerical tests (#156)

    Continuation of clean up of stella. The kxky grids have been cleaned up, and separated out into different modules. There not exists a <parameters_kxky_grids.f90> file which is the overarching module that reads the parameters for the kxky grids. This then uses either <parameters_kxky_grids_box.f90> or <parameters_kxky_grids_range.f90> depending on which grid type is chosen in the input file. Two additional modules have been added as a result of this split up called <calculations_kxky.f90> and <write_radial_grid.f90>.

    There is a new folder called <grids_kxky.f90> file that initialised the kxky grids and fills the arrays for the kxky grids.

    The parameter namelist have also been changed, and placed into different modules. The new files are <parameters_numerical.f90> <parameters_physics.f90>, and have replaced the previous modules <run_parameters.f90>, <physics_flags.f90>, <physics_paramters.f90>. These have been named in preparation for organising stella into sub directories.

    A new debug feature has also been added to allow the debug flags to be turned on/off in the input file, rather than requiring the code to be re-compiled. This is found in <debug_flags.f90>.
Merge branch 'master' into New_cleanup_fields