split versioned plugin doc generation ci job into two

[jsvd]

currently the ci job to generate docs performs the following tasks:

1. generates docs for all plugins
2. clones docs repo and tests generated plugin docs
3. creates creates a PR if generation is sucessfull

The problem with this approach is that, if there's an error with the docs, the PR is never created so there's no easy way to work on the broken PR to make it work. So instead we should have two ci jobs:

1. One that periodically computes new docs and creates a PR
2. Another that takes a PR and tests against the docs repository