[Change Proposal] support specifiying alternate data_stream.dataset

For REST APIs we would really like to have a single meta package where
we can define an input multiple times and in that input redirect the
data to a different `data_stream.dataset`. For example if the REST
API contained both Apache Access and AWS Cloudtrail data two inputs
would be defined. In addition to the variables needed to connect to
the REST API and collect the data, each input would also have an
option to select the `data_stream.dataset` from a list of available
`data_stream.dataset`s This would allow you to send the Apache Access
data from the REST API to the `apache.access` dataset and take
advantage of the ingest node processing available. It would also
allow you to take advantage of the Apache Dashboards.

This new field would signal to Kibana to display a list of available
`data_stream.dataset`s for the user to pick from. Also if a dataset
is selected Kibana would need to "install" that package so that the
ingest pipelines and dashboards are available.

This could be useful for kafka and syslog as well.