Use Kokkos::abort() in DEAL_II_NOT_IMPLEMENTED().

[bangerth]

This is a necessary follow-up to #16543: As mentioned in #16543 (comment), we can't use std::abort() on devices. Instead, we must use Kokkos::abort("text");.

For reference, Assert is currently defined in the following way:

#  if KOKKOS_VERSION >= 30600
#    ifdef DEAL_II_HAVE_BUILTIN_EXPECT
#      define Assert(cond, exc)                                                \
        do                                                                     \
          {                                                                    \
            KOKKOS_IF_ON_HOST(({                                               \
              if (__builtin_expect(!(cond), false))                            \
                ::dealii::deal_II_exceptions::internals::issue_error_noreturn( \
                  ::dealii::deal_II_exceptions::internals::ExceptionHandling:: \
                    abort_or_throw_on_exception,                               \
                  __FILE__,                                                    \
                  __LINE__,                                                    \
                  __PRETTY_FUNCTION__,                                         \
                  #cond,                                                       \
                  #exc,                                                        \
                  exc);                                                        \
            }))                                                                \
            KOKKOS_IF_ON_DEVICE(({                                             \
              if (!(cond))                                                     \
                Kokkos::abort(#cond);                                          \
            }))                                                                \
          }                                                                    \
        while (false)