Make Ifpack2::RILUK have a proper reuse capability.
Created by: ambrad
@trilinos/ifpack2, @mhoemmen , @srajama1
RILUK's symbolic-phase information cannot be reused right now. Users must call initialize() before compute(), always. See, e.g., the logic surrounding #define IFPACK2_HAS_PROPER_REUSE in MueLu_Ifpack2Smoother_def.hpp. This issue is focused on making RILUK have a proper symbolic/numeric/apply division of labor and so a reuse capability.