Add system API for building document URI with user ID.

This is required for the direct tabbed DocsUI experience that doesn't
involve the up-front disambig (that always only has one app in it).

Bug: 145895146
Bug: 147900456
Test: atest CtsProviderTestCases:android.provider.cts.DocumentsContractTest
Change-Id: Ic44b592382d880cdd76df2885ca8c52b1b697697