Add support for setting a version tag for a Form

[jfriedenstab]

Problem you would like to solve

As a Camunda 8 user, I'd like to be able to specify a custom version tag for a Form (so that the Form will be available under this version tag when it gets deployed later on and can be referenced from a BPMN user task using versionTag binding).

Proposed solution

• A new (optional) input field "Version tag" is added to the "General" section of the properties panel for a Form.
• The version tag is stored in a new versionTag JSON property:

{
  "id": "Form_1",
  "type": "default",
  "versionTag": "v1",
  "components": [],
}

Additional context

• part of [EPIC] Support version tag binding for linked resources camunda#19812
• relates to Add support for versionTag binding for user tasks #4462

[philippfromme]

Ready to be integrated into both modelers once bpmn-io/form-js#1243 is released.