Activate `requires-plugins` from a project without using `poetry install`

Issue Kind

Change in current behaviour

Description

I have a use case where I currently copy the pypoetry.toml and poetry.lock files into a docker container and then run poetry export. In order to install the export plugin, I looked at using the tool.poetry.requires-plugins section, but it looks like that's only checked when the project is installed. It'd be nice if there was a way to ensure all required project plugins were installed without installing the project itself. That could either be a new command or maybe poetry self install could be changed to install project plugins as well.

Impact

This would improve the flexibilty of the tool.poetry.requires-plugins configuration option.

Workarounds

I worked around the issue by installing poetry-plugin-export explicitly in my dockerfile, but it'd be nice if there was a more generic way to accomplish this.