* realization.get_smry() has changed to always return a dummy index
* cache_eclsum is pruned from fmu-ensemble.

The argument column_keys is no longer accepted by get_smry_meta().
All smry metadata available to a realization/ensemble is now always
returned by this function.

This function is no longer the recommended practice for a client script
to obtain the relevant summary vector metadata, API users should use
the attrs["meta"] property of the returned summary dataframes instead.

ensemble.get_smr() will no longer ensure that the dates returned
are identical in all realization, realizations with shorter timespans
will not be extrapolated as they were before.

This also affects get_smry_stats(), for which realizations
which failed prematurely earlier had zero rates, affecting statistical
profiles. Now these realization with truncated time-series will only
affect the statistical profiles in the time-range they have data for.