Improve Performance of Multipart Body

Current Issue

• Processing a large multipart body might cause the app hang
• Export Multipart with the incorrect file extension
• Proxyman always processes the Multipart data multiple times for the same body -> Waste CPU
• Multipart tab shows old data even though we select a new request

Acceptance Criteria

• Improve performance when processing a large Multipart data
• Respect the original file extension when exporting
• Don't process the same Multipart Data
• Fixed: The Multipart tab shows old data even though we select a new request

Env

• Proxyman macOS 4.13.0