* Update shared files to support versioned plugin docs
test
* Make common files work for LS Ref and versioned plugin ref
* Remove plugin name from TOC entry
* Remove plugin-intro because it needs to live in logstash-docs only
* Edit common files
This PR is based on the proposal from #6846, it does the following
- Change the format of the plugin help page
- Create an external file for each plugin type that will get included by the plugin
- Add a script to generate the PR on each plugin repo with the static doc
- Add a script `ci/ci_docs.sh` that will be used to generate the list of plugins that can be installed in logstash from all the available plugins from the community organization
This PR is the building block for change in https://github.com/elastic/docs-tools/issues/3Fixes#6941