Feat/agentflow add support for Variable System & Syntax Support (#6067)

* Initial flow

* Add tiptap - mention dependency similar to v2

* Add functionalities similiar to V2

* update to tiptap to 3.20.4

* Fix lint error

* Added missiing test cases for new files

* Styling changes

* InputMessage should be visible on initial load

* Fix gemini comment

* Remove outdated SelectVariable

* Add icon support similar to v2

* Fix gemini comments

* Remove input folder and utils folder under atoms

* Fix test error

* Fix initlalDefualts not being set

* Fix after merge with main

* Fixes for review comments

* Fix review comments

* New test cases added for fixes

* Remove additional space