This makes it possible for encoders to output better representation
of the actual objects instead of working with chopped up segments.
* IAnsiConsole.Write now takes an IRenderable instead of segments
* Calculating cell width does no longer require a render context
* Removed RenderContext.LegacyConsole
* Removed RenderContext.Encoding
* Added Capabilities.Unicode
These methods don't require a string.format call so we'll directly call the Render method without a call to string.format.
Added bonus of a a couple fewer allocations too.
