[WIP] Web Modeler support

[marstamm]

Product hub Epic: https://github.com/camunda/product-hub/issues/2703

Changes needed in Frontend

• Expand task testing to support plugins
• Add html log viewer
• Add isTesting flag to supplied process variables when testing RPA tasks
• (optional) filter internal variables (isTesting flag, document descriptor for log)
• Linking RPA tasks and appending through append anything menu

Changes needed in RPA worker

• check for a isTesting flag in process variables
• Upload log.html to document storage at the end of execution. Even if execution failed

Web-Modeler Backend

• Allow Uploading and Storing RPA files
• We can probably re-use a lot of the Form files