private_endpoints_service: wait for all regions

[carloruiz]

Previously, when waiting for private endpoints service creation, the resource could be considered ready if a single resource was ready and others were not yet created. This commit fixes the bug by explicitly waiting for all regional services to be AVAILABLE.

Commit checklist

• [ ] Changelog
• [ ] Doc gen (make generate)
• [ ] Integration test(s)
• [ ] Acceptance test(s)
• [ ] Example(s)