### What problem does this PR solve?
Feat: Add StringTransform operator #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Customize the output variable name of the loop operator #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Filter the query variable drop-down box options by type #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Add IterationNode component #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Let system variables appear in operator prompts #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Constructing query parameter options for the Retrieval operator
#3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Feat: Construct RetrievalForm with original fields #3221
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
