Mathematics good first issues

Rename existing CMake configuration options in the Spheral++ project that follow the pattern `ENABLE_XXX` to `SPHERAL_XXX`. Additionally, ensure that compile-time definitions referenced in the source code match the corresponding CMake variable names, maintaining consistency with changes made in issue #379. This involves reviewing and updating CMakeLists.txt files and source code.

Investigate if compiling Spheral's 1D, 2D, and 3D instantiations into a single file significantly improves parallel build times on Lawrence Livermore National Laboratory (LLNL) systems. This involves measuring compile times with the current separate instantiation files and comparing them to compile times with a consolidated file.

Rename the CMake variable `ENABLE_CXXONLY` to `SPHERAL_ENABLE_PYTHON` and refactor the codebase to use the new variable consistently. This improves code readability by making the conditional logic for Python bindings more explicit.