Replace DUNE_VERSION_NEWER with DUNE_VERSION_GTE.
This MR introduces new macros with endings GTE, GT, LTE, and LT to replace the NEWER macros which have misleading names. Also, a unit test was added.
Since these macros are used to check versions of the DUNE core modules I propose to backport to DUNE 2.4 and then deprecate DUNE_VERSION_NEWER after the 2.6 release.