Add support for toggling taskbar

- Use new API to enable/disable SysUI taskbar integration
- User-facing setting to control taskbar eligibility
- Reload by restarting (live reload would be much more complicated)
- Update SysUI integration state before reloading

Depends on frameworks/base commit:
    SystemUI: Add API for runtime taskbar config

Change-Id: Id1889ca9b102f94cc0a1161f49de88428dcc0943