Transport Tester GUI App: add support for generic transport, send report, UI polish

[amircybersec]

This PR replaces PR #137; since I had to rebase and refactor the PR #137 that it got a bit out of hand and decided to cherry pick commits into a clean branch off main. Here's is the summary of changes made to the Transport Tester GUI App:

CHANGELOG:

• Add a new optional report collector URL field to the GUI (shared front-end)
• Submit reports to a remote destination using report package (shared backend). One simple approach to set up a remote collector using Google Spreadsheet is discussed here.
• Add support for existing SDK transports and wrapping (e.g. split, socks5, tls, ss, etc)
• Redact UserInfo from transports in reports, e.g.: ss://[email protected]:65496
• Include transport specific setup errors (e.g. split not supported over udp) in response error field
• Display error message on the GUI (front-end)
• Renamed app to Transport Tester
• Add Powered By Outline logo
• Add popover to show information for each field