Filter unsupported tracker URLs from magnets

[TurboTheTurtle]

Closes #23937.

Filters unsupported tracker URLs while parsing magnet links so only tracker schemes accepted by libtorrent are added to the torrent descriptor.

Manual validation:

• Tested on macOS 27.0 (26A5353q), arm64, Qt 6.11.1, local Debug build.
• Added a magnet link containing valid http and udp trackers plus invalid encoded HTML, ftp, and numeric tracker values.
• Verified the Trackers tab only listed the valid http://tracker.example.com/announce and udp://tracker.example.com:1337/announce entries.
• Verified the invalid tracker values were not added and no Unsupported URL protocol tracker entries appeared.