Chained variables

[heidmotron]

What does this PR do?

• Adds support for chained template variables.
• Allows for scopedVariables to override template variables when a panel has a repeat option set

How does this impact users?

Users can now create template variables with UQL filter expressions. Those filter expressions can have template variables as well.

For example, when a service variable exists and we're defining an operation variable we can make it dependent on the service variable with the following UQL filter expression:

service == $service

This will then scope the operation values to the value(s) in $service

What needed to change in the code and why?

• Introduced a new form element for updating the scope expression
• When requesting attributes values, we'll always serialize the template variables like we do when querying.

How did you test this?

Manual

[DHedgecock]

Oh nice, this is a great simple way to provide this 🏆

[DHedgecock]

🎉 awesome upgrade