### What problem does this PR solve?
Feat: Add insert variable icon in the header of prompt editor. #4764
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Fixed the issue where the prompt always displayed the initial
value when switching between different generate operators #4764
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Add VariablePickerMenuPlugin to select variables in the prompt
text box by menu #4764
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
