ENH: Update highspy bindings and cleanup meson.build for SciPy

[HaoZeke]

One part of #1987. Basically after #1997 there are still some more warnings needed for SciPy to be happy scipy/scipy#21565; but that'll be in a follow up as per @galabovaa 's suggestion #1987 (comment) and.

The changes here are (as seen in each commit message, summarized here):

• Fixes to remove unused variables within highs_bindings.cpp
  • Also cleaned up the export_values situation with a code comment
• Adding enums used by SciPy but not currently present in highspy:
  • HighsDebugLevel
  • SimplexCrashStrategy
• Removed HighsOptionsManager, which I added explicitly for the SciPy bindings
  • It isn't used by highspy internally, so should live in scipy anyway

The only other changes (not really enumerated) are those to the meson.build; and are essentially just to keep the built libraries up to date and compatible with SciPy.

Next steps:

• I'll open a series of PRs, one per warning to be removed (since they can seem intimidating otherwise)
  • If any of them seem dodgy we can close them and I'll just suppress them in the SciPy meson.build
• I'll then rebase the SciPy HiGHS fork and have that merged in
  • Unfortunately as noted by @rgommers MAINT: Updating HiGHS to match latest -- II scipy/HiGHS#68 (comment) the fork and upstream cannot get much closer
    • The branch history in the fork includes a lot of other commits which aren't relevant so can't be part of a PR to upstream (see MAINT: Updating HiGHS to match latest scipy/HiGHS#67)

[jajhall]

Happy for the Meson build changes to be made, as this is no longer supported by HiGHS

In src/highs_bindings.cpp, I'd like @mathgeekcoder to review the removal of data from highs_setCallback.

The code to make enum SimplexCrashStrategy available to highspy should be removed, as there is no longer any code in HiGHS for a simplex crash strategy. I'll delete it from lp_data/SimplexConst.h - which, I believe, doesn't need to be included, since the values of enum SimplexEdgeWeightStrategy were obtained via #include "Highs.h"

[mathgeekcoder]

In src/highs_bindings.cpp, I'd like @mathgeekcoder to review the removal of data from highs_setCallback.

Thanks Julian. The change to setCallback looks good to me!