Tag-Lists (with auto completion) instead of comma-seperated lists

[christian-konrad]

Is your feature request related to a problem? Please describe

In the properties panel, you oftentimes need to specify a comma-seperated list when you enter multiple property values, for example the delegated users of a user task. Comma-seperated lists are prone to errors and inconvenient for users, even for developers. Furthermore, if we want to provide a way for Form builders to set defaults for a multi-select component (checkbox or tag list), this must also be scalable and provide the selectable values for the user to select.

Describe the solution you'd like

A new tag-list input type for all list-based properties with autocompletion/-suggestion if there are values to select from.

Describe alternatives you've considered

Sticking to comma-seperated lists and taking the risk of telling the user implicitly "we don't care about your UX"

Additional context

Related to #492
Related to / duplicate of bpmn-io/properties-panel#223

[christian-konrad]

Ignore now, maybe build later (when we need it in Forms or get bad feedback for current comma-seperated lists)