Request: Add a gradle plugin task to put the emulator into demo mode

[DanielJette]

Is your feature request related to a problem? Please describe.

Add a testifyDemoMode command. ./gradlew testifyDemoMode

Demo mode for the status bar allows you to force the status bar into a fixed state, useful for taking screenshots with a consistent status bar state, or testing different status icon permutations. Demo mode is available in recent versions of Android.

https://android.googlesource.com/platform/frameworks/base/+/master/packages/SystemUI/docs/demo_mode.md

This feedback relates to:

• [ ] The Kotlin library
• [x] The Gradle plugin
• [ ] The IntelliJ Platform plugin
• [ ] The sample code
• [ ] The documentation