Add x-pack role to relevant metricsets

[dedemorton]

Describe the enhancement:
Currently we only mark modules with the x-pack flag. This is likely to confuse users especially now that we have an Integrations page that sends users directly to the metricset docs.

We need to add the x-pack role to every metricset that is in an x-pack module.

Describe a specific use case for the enhancement or feature:
Users who enter the docs through the Integrations page end up on a page that doesn't make much sense.

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)