Export summary

Problem/Motivation

The existing drush exports (XML & JSON) provide a fairly verbose description of each of the reasons for each project not being compatible with the next major version.

I'd love to be able to export a summary. I'd like to be able to track the status of multiple upgrades across a number of different clients in a dashboard, and being able to export simple information such as the % complete, environment compatibility, remove, update, collaborate and fix manually counts as part of the CI/CD process would help with this.

Proposed resolution

Add a new drush command such as 'upgrade_status:summary', or 'upgrade_status:analyze --summary' to export the basic high level information.