Evaluate automating docs generation for aliased plugins

[karenzone]

In 7.x, we introduced the concept of plugin aliases with input-elastic_agent->input-beats.
Here's the meta issue: elastic/logstash#12794.

Plugin docs rely on a version bump and a published gem for new docs to picked up. Currently, moving the generated content from beats to elastic_agent involves a manual copy-paste and changes to attributes.

Here's an example of the manual work required: elastic/logstash-docs#1310. This example is for the 7.17 branch, but this work is required for any branch on which input-beats is updated.