Changes:
* Renames 'full copy searchable snapshot' to 'fully mounted index.'
* Renames 'shared cache searchable snapshot' to 'partially mounted index.'
* Removes some unneeded cache setup instructions for the frozen tier. We added a default cache size with #71844.
* Remove frozen tier restriction for ESS
* Remove section from 'Use ES for time series data'
Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>
Removes the experimental status for the frozen tier / shared_cache searchable snapshots for the 7.13 release.
Also adapts docs that URL repositories are now supported in 7.13 for searchable snapshots.