Connectors: Allow hyphens in connector IDs

Expands the connector ID validation regex from `/^[a-z0-9_]+$/` to `/^[a-z0-9_-]+$/`, aligning with the PHP AI Client library naming conventions. Hyphens are normalized to underscores when generating `setting_name` (e.g., `azure-openai` → `connectors_ai_azure_openai_api_key`).

Developed in https://github.com/WordPress/wordpress-develop/pull/11285.

Props pers, gziolo, jorgefilipecosta, westonruter, flixos90, mukesh27.
Fixes #64861.



git-svn-id: https://develop.svn.wordpress.org/trunk@62056 602fd350-edb4-49c9-b593-d223f7449a82