Allow navigating to Flutter screen from within Ensemble

[kmahmood74]

copied from discussion -

Use case:

I have an existing Flutter app that I want to add Ensemble screens to
From an Ensemble screen I want to navigate to a Flutter screen
Example:

- Button:
          label: Navigate and pass inputs to a Flutter screen
          onTap:
            executeCode:
              body: |
                //@code
                ensemble.navigateFlutterScreen(
                  'MyFlutterWidget', # this is my screen's name
                  { # and here are the constructor parameters
                    'input': someInput 
                  }
                );

• You should be able to do this directly in the navigateScreen action as well without having to write code.
• Support the same for showModal action as well
• Support the other way around too i.e. navigating to an Ensemble screen from Flutter
• As the first step, propose the yaml and the corresponding javascript syntax before proceeding with the implementation

[kmahmood74]

assigning to @vusters for assessment and re-assignment

[kmahmood74]

cc @snehmehta @vusters

[kmahmood74]

@snehmehta please update, this was completed a while ago I thought?