WordPress 7.0 compatibility

[martin-helmich]

This is an umbrella issue for asserting that this plugin is compatible with WordPress 7.

Items:

• Use the new native AI connectors
• Drop dependency to AI Experiments plugin
• Raise minimum requirement (Requires at least field) to WordPress 7

See https://wordpress.org/support/topic/requires-ai-experiments-but-wordpress-7-0-has-native-connectors

[martin-helmich]

This is partially completed; release v0.2 dropped the dependency to the AI Experiments plugin, but there are still some BC hacks for 6.9 compatibility, and we should still check how well the provider integrates into the connector UI (probably in 7.0-beta3).