Add new method to update Layer2 information when L2 roaming happens.

This change adds an new method updateLayer2Information in IIpClient.aidl
to update layer2 info (e.g. bssid, l2key and grouphint) to detect whether
L2 roaming happens or not.

Bug: 131797393
Test: atest NetworkStackTests FrameworksNetTests
Change-Id: I20ba0d94a486378bb5b7a318a338746655deb4ff