Fix propagation of RouteDiscoveryPreferences active scan flag

- This caused provider apps to be always scanning to make sure the UI has up to date information. This can result in unnecessary network scans, which can impact other devices on the network's ability to enter sleep mode for power savings, which is a critical issue, especially in European markets where regulations are strict around requirements for TV sleep modes.
- The solution was to propagate the flag through the framework as for providers (isActiveScan = isAnyRouterScanning || isManagerScanning);

Bug: 250024338
Test: manually by adding logs in onDiscoveryRequestChanged in the MediaRouting Androidx demo
Change-Id: I8dece5f5792dccb8df3db497b3b5bdceedede6a3