Update IPv8 pointer and tests

[qstokkink]

This PR:

• Updates IPv8 to the 3.0 version.
• Updates the Tribler tests to use a single MockTriblerConfigManager class.
• Updates the Tribler tests to use the IPv8 MockRequest class.
• Updates the ruff configuration to use Python 3.9+ syntax.
• Updates the ruff GitHub Action to ignore changed files in the pyipv8 submodule.

[qstokkink]

This is technically ready for review, but I won't merge it until after the 8.0.7 release.