VirtualDevice clipboard support

This CL refactors ClipboardService to provide siloed clipboard storage
for VirtualDevices, adding an additional dimension for selecting clip
storage alongside the existing userId dimension.

This behavior is turned off by default behind a DeviceConfig flag.

Bug: 262038440
Test: atest ClipboardManagerTest ClipboardManagerListenerTest StreamedAppClipboardTest
Change-Id: I88de5a9930448f741169cd48d3804a9d936dfa76