Resolve "single function to generate all the folders relative to root_dir"

Closes #47 (closed) create a utility get_important_folders(root_dir) that returns the

release_base_dir = root_dir / mpsd_release
package_set_dir = release_base_dir / microarch  # Here lies spack and lmod folders 
spack_setup_script = release_base_dir / "spack-environments" / "spack_setup.sh"
lmod_dir = package_set_dir / "lmod"
logs_dir = root_dir / mpsd_release / "logs"

etc

This is so that in the future when there is a need to change the folder structure, not all methods need to be updated.