Revert "DevelopmentSettings: Allow using Classic WebView"

This reverts commit 03283ef447a37e65f6f3c2e84127ee096024c364.
Revert "Revert "[2/2] ElectronBeam: Add an alternative screen-off animation""

This reverts commit 7248d79bd918105e6bba4091828f2a24863cd2e9.