Moved analyzer tests to its own project

Also moves tests to `./test` which makes it possible
for all test projects to share the same .editorconfig
files and similar.

test/Spectre.Console.Tests/Unit/RenderHookTests.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+using System.Linq;
+using Shouldly;
+using Spectre.Console.Rendering;
+using Spectre.Console.Testing;
+using Xunit;
+
+namespace Spectre.Console.Tests.Unit
+{
+    public sealed class RenderHookTests
+    {
+        private sealed class HelloRenderHook : IRenderHook
+        {
+            public IEnumerable<IRenderable> Process(RenderContext context, IEnumerable<IRenderable> renderables)
+            {
+                return new IRenderable[] { new Text("Hello\n") }.Concat(renderables);
+            }
+        }
+
+        [Fact]
+        public void Should_Inject_Renderable_Before_Writing_To_Console()
+        {
+            // Given
+            var console = new TestConsole();
+            console.Pipeline.Attach(new HelloRenderHook());
+
+            // When
+            console.Write(new Text("World"));
+
+            // Then
+            console.Lines[0].ShouldBe("Hello");
+            console.Lines[1].ShouldBe("World");
+        }
+    }
+}