Add entries for Transcode Settings in Dev Options

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

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

Test: Manual
Bug: 169547037
Change-Id: I2762da7535f441a85ae5ad01df3d6a328502c962