Docs: Update s3 repository docs with client settings (#26033)
Docs: Update s3 repository docs with client settings (#26033)

This commit updates the s3 repository docs to clearly mark settings as
part of the s3 client settings, as well as those that are secure and
must be stored in the elasticsearch keystore.

relates #25619

vroyer/elasticassandra,strapdata/elassandra,vroyer/elassandra,vroyer/elasticassandra,vroyer/elasticassandra,strapdata/elassandra,strapdata/elassandra,vroyer/elassandra,vroyer/elassandra,strapdata/elassandra,strapdata/elassandra