Improves the Parquet File Output transform and adds test coverage for the output package

[leehaut]

Fix #7047

• UI: Fix vertical alignment of the Base file name label, text field, and Browse button in ParquetOutputDialog.
• Behavior: When no fields are configured, output all input fields automatically (same pattern as Text File Output).
• Tests: Add unit tests for output classes (excluding the dialog), including a resource-based round-trip test that reads hello.parquet-00-0001.parquet from test resources.