`ios_app_clip` should validate that `application-identifier` is set in entitlements

[brentleyjones]

Xcode automatically sets application-identifier in an App Clip's entitlements. If it's not set, then app clips fail to install because (null) is not a prefix of whatever com.apple.developer.parent-application-identifiers is set to. Ideally it should validate that com.apple.developer.parent-application-identifiers is set as well, and that application-identifier is a prefix of it.