Add Transcode Settings screen in Developer Options

This screen would be used to enable/disable transcoding for all apps, and select a list of apps to be skipped from transcoding.
UI screenshot: https://screenshot.googleplex.com/4bpbZdM6vbhdw5u

Design doc reference for native transcoding: go/seamless-transcoding

Test: Manual
Bug: 169547037
Change-Id: I7cf72131560b99728083838bf0dad400bb5cb4a9