Create provider instances for AI povider plugins. Each provider plugin can now have multiple instances, allowing for different configurations and models using the same base provider.
Co-authored-by: Meirza <meirza.arson@moodle.com>
Initial implementation of the LMS AI subsystem. Originally implemented in MDL-80889 Co-authored-by: Meirza <meirza.arson@moodle.com>