exercises need to be updated for latest Catalyst & MTK releases #70
Description
Catalyst has just updated to a new (breaking) major release, switching from MTK v9 to the new ModelingToolkitBase (the base for MTK v11). As Catalyst was the package restricting MTK to the older v9 version, the entire project can now update to the latest (breaking) MTK version as well.
A quick browse through Catalyst's release notes makes the switch to the latest version seem worthwhile. Note that starting from the v11 version of ModelingToolkit, advanced functionality such as automated index reduction has been split into separate packages which are now AGPL licensed. We should check whether this is a problem, and whether the MIT licensed base ModelingToolkitBase is sufficient for the course.