Added workaround for deprecation of macos-12 runner

[qstokkink]

Fixes #8200

This PR:

• Updates the unit tests to use macos-14 instead of macos-12.
• Updates create_torrent_file to use the v1_only flag.
• Removes macos-12 from the build job.

[qstokkink]

It seems like the newest libtorrent version demands a minimum piece size of 16384 for v2-compatible torrents. From the libtorrent source, I gather that passing the v1_only flag may fix this.

https://github.com/Tribler/tribler/blob/04095a69300311018d0a8fb7f730b2090ee3ffb3/src/tribler/core/libtorrent/torrents.py#L152

That said, this flag is so new that it doesn't exist on our typing yet, or in lt.create_torrent_flags_t, and we'll have to manually insert the integer value.

UPDATE: This is a confirmed fix.