Create seamless top app bar colour

[alyblenkin]

Part of app bar rework #6320

We want to ensure we have a seamless colour shared with the app bar and status bar so we don't get the zebra stripe at the top.

The M3 doc says the easiest way is to enable displaying content edge-to-edge: https://github.com/material-components/material-components-android/blob/master/docs/components/TopAppBar.md#status-bar-and-edge-to-edge