Add global usings (#668)

* Use global usings

* Fix namespace declarations for test projects

src/Spectre.Console/Internal/Backends/Ansi/AnsiBuilder.cs

@@ -1,7 +1,3 @@
-using System;
-using System.Linq;
-using System.Text;
-using Spectre.Console.Rendering;
 using static Spectre.Console.AnsiSequences;
 
 namespace Spectre.Console;

src/Spectre.Console/Internal/Backends/Ansi/AnsiColorBuilder.cs

@@ -1,7 +1,3 @@
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-
 namespace Spectre.Console;
 
 internal static class AnsiColorBuilder

src/Spectre.Console/Internal/Backends/Ansi/AnsiConsoleBackend.cs

@@ -1,5 +1,3 @@
-using System;
-using Spectre.Console.Rendering;
 using static Spectre.Console.AnsiSequences;
 
 namespace Spectre.Console;

src/Spectre.Console/Internal/Backends/Ansi/AnsiConsoleCursor.cs

@@ -1,4 +1,3 @@
-using System;
 using static Spectre.Console.AnsiSequences;
 
 namespace Spectre.Console;

src/Spectre.Console/Internal/Backends/Ansi/AnsiDecorationBuilder.cs

@@ -1,5 +1,3 @@
-using System.Collections.Generic;
-
 namespace Spectre.Console;
 
 internal static class AnsiDecorationBuilder

src/Spectre.Console/Internal/Backends/Ansi/AnsiDetector.cs

@@ -1,9 +1,3 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Runtime.InteropServices;
-using System.Text.RegularExpressions;
-
 /////////////////////////////////////////////////////////////////////////////////////////////////////
 // Portions of this code was ported from the supports-ansi project by Qingrong Ke
 // https://github.com/keqingrong/supports-ansi/blob/master/index.js

src/Spectre.Console/Internal/Backends/Ansi/AnsiLinkHasher.cs

@@ -1,6 +1,3 @@
-using System;
-using System.Runtime.CompilerServices;
-
 namespace Spectre.Console;
 
 internal sealed class AnsiLinkHasher

src/Spectre.Console/Internal/Backends/Ansi/AnsiSequences.cs

@@ -1,5 +1,3 @@
-using System.Linq;
-
 namespace Spectre.Console;
 
 internal static class AnsiSequences

src/Spectre.Console/Internal/Backends/AnsiConsoleFacade.cs

@@ -1,6 +1,3 @@
-using System;
-using Spectre.Console.Rendering;
-
 namespace Spectre.Console;
 
 internal sealed class AnsiConsoleFacade : IAnsiConsole

src/Spectre.Console/Internal/Backends/IAnsiConsoleBackend.cs

@@ -1,5 +1,3 @@
-using Spectre.Console.Rendering;
-
 namespace Spectre.Console;
 
 /// <summary>

src/Spectre.Console/Internal/Backends/Legacy/LegacyConsoleBackend.cs

@@ -1,5 +1,3 @@
-using Spectre.Console.Rendering;
-
 namespace Spectre.Console;
 
 internal sealed class LegacyConsoleBackend : IAnsiConsoleBackend