Checking for plugin updates: Show current version + new version

[swashbuck]

Subject of the enhancement

When checking to see what plugins can be updated, it would be useful to see the current version of a plugin plus the new version that it will be updated to. The current version is already shown when not using --check.

Steps to reproduce

Run adapt update --check

Expected behaviour

In the report, plugins that will be updated show what the current version is:

The following plugins will be updated:
adapt-contrib-accordion from 7.6.3 to 7.6.4 (latest compatible version is 7.6.4)
adapt-contrib-confidenceSlider from 5.5.2 to 5.5.3 (latest compatible version is 5.5.3)

Actual behaviour

Current plugin version is not shown:

The following plugins will be updated:
adapt-contrib-accordion 7.6.4 (latest compatible version is 7.6.4)
adapt-contrib-confidenceSlider 5.5.3 (latest compatible version is 5.5.3)