parse userId from authority in opp in the same way as ContentProvider

Ensures that userId determination is consistent with ContentProvider

Bug: 395647005
Bug: 395643490
Flag: EXEMPT fix for vulnerability
Test: m com.google.android.bt
Test: atest BluetoothJavaUnitTests:com.android.bluetooth.opp.BluetoothOppSendFileInfoTest
Ignore-AOSP-First: fix for undisclosed vulnerability
Change-Id: I7b6affec5dada7c9f0319fbdb35a6e977e51990f