Fix/agentflow Fixing agentflow UI style and make it similar to v2 (#6280)

* Fix output node not selectable

* Fix highlight color

* Fix previous node displaying label and not ID

* Fix tool arguements not being called

* Fix dropdown values to not be bold

* Add standard sizing for all input text

* FIx syntax highlighting styling

* Use predefined tokens for font weight and size

* Fix dialog size of Source

* Fix color of syntax highlight in dark mode

* Fix the input fileds color in dark and regular mode

* Fix gemini comments

* FIx inconsistent spacing

* Standardise gap between label and field

* Remove export for unused function and standardize dialog size accrosss code, rich text,
  and source

* Fix test error