Modify route creation metrics in extension DIAL MRP

Another attempt at making histograms measure the same thing in the extension and native DIAL MRPs.
The native MRP only measures success after receiving the app launch result, so we should do the same in the extension.

https://cs.chromium.org/chromium/src/chrome/browser/media/router/providers/dial/dial_media_route_provider.cc?l=337&rcl=26b43e5efbb0b3b20e55184087f379a167fa2b4c

PiperOrigin-RevId: 257856410
1 file changed