Change IAnsiConsole to render IRenderable

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

examples/Console/Info/Program.cs

@@ -11,6 +11,7 @@ namespace InfoExample
                 .AddColumn()
                 .AddRow("[b]Enrichers[/]", string.Join(", ", AnsiConsole.Profile.Enrichers))
                 .AddRow("[b]Color system[/]", $"{AnsiConsole.Profile.ColorSystem}")
+                .AddRow("[b]Unicode?[/]", $"{YesNo(AnsiConsole.Profile.Capabilities.Unicode)}")
                 .AddRow("[b]Supports ansi?[/]", $"{YesNo(AnsiConsole.Profile.Capabilities.Ansi)}")
                 .AddRow("[b]Supports links?[/]", $"{YesNo(AnsiConsole.Profile.Capabilities.Links)}")
                 .AddRow("[b]Legacy console?[/]", $"{YesNo(AnsiConsole.Profile.Capabilities.Legacy)}")

examples/Console/Tables/Program.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics;
 using Spectre.Console;
 
 namespace TableExample