Refactors `ChatLine` component to use more sensible override properties
and layout using grid container. Moves creation of username component
into its own method to simplify BDL.
Updates padding of base `DrawableChannel` flow padding.
Removes usage of `ChatOverlayDrawableChannel` since it's overrides are
no longer needed.
Updates usage of `StandAloneChatDisplay` to use new override properties
of `DrawableChannel`.
Also removes the necessity of scheduling as it actually never worked as
intended, `Scheduler` will still update even when the chat line is
masked away, and the animation will never be held anyways.
The new duration of the animation should be enough for long scrolls
either way.