Fix anr issue on connected devices settings

Before this CL, connected devices settings will use ContentResolver
to get advanced device bitmaps on the UI thread. It will have a little
chance to cause ANR.

This CL uses background thread to get a bitmap to fix ANR issue.

Bug: 173283590
Test: Test: make -j42 RunSettingsRoboTests
Change-Id: I987759a775d507003fd4ef54f5376bd24e660b3b