Feature parity between the plugins/ bind mount and PLUGINS environment variable

### Enhancement Type

Improve an existing feature

### Describe the enhancement

I've been using the PLUGINS enviroment variable to deploy "packages" of plugins to my servers, but the PLUGINS feature only copies .jar files instead of copying all files like the `/plugins` bind mount. I was wondering if we could get an option to have feature parity between the two so I can deploy and interpolate plugin configuration along with the jar files in packages.

I'm doing things this way as some of my servers require different "packages" of plugins, eg, a creative world not requiring survival-orientated plugins, but multiple survival worlds all requiring the same survival plugin config.


Start by tracing how the PLUGINS environment variable is handled and how the /plugins bind mount is populated at startup. Compare the two paths for plugin packages and configuration files; done means PLUGINS can deploy the same relevant files and configuration as the bind mount.

Written by the indexing model from the issue text.