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.Analyzer.Tests/Unit/Analyzers/UseSpectreInsteadOfSystemConsoleAnalyzerTests.cs

@@ -0,0 +1,67 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Testing;
+using Xunit;
+
+namespace Spectre.Console.Analyzer.Tests.Unit.Analyzers
+{
+    public class UseSpectreInsteadOfSystemConsoleAnalyzerTests
+    {
+        private static readonly DiagnosticResult _expectedDiagnostics = new(
+            Descriptors.S1000_UseAnsiConsoleOverSystemConsole.Id,
+            DiagnosticSeverity.Warning);
+
+        [Fact]
+        public async void Non_configured_SystemConsole_methods_report_no_warnings()
+        {
+            const string Source = @"
+using System;
+
+class TestClass {
+    void TestMethod() 
+    {
+        var s = Console.ReadLine();
+    } 
+}";
+
+            await SpectreAnalyzerVerifier<UseSpectreInsteadOfSystemConsoleAnalyzer>
+                .VerifyAnalyzerAsync(Source)
+                .ConfigureAwait(false);
+        }
+
+        [Fact]
+        public async void Console_Write_Has_Warning()
+        {
+            const string Source = @"
+using System;
+
+class TestClass {
+    void TestMethod() 
+    {
+        Console.Write(""Hello, World"");
+    } 
+}";
+
+            await SpectreAnalyzerVerifier<UseSpectreInsteadOfSystemConsoleAnalyzer>
+                .VerifyAnalyzerAsync(Source, _expectedDiagnostics.WithLocation(7, 9))
+                .ConfigureAwait(false);
+        }
+
+        [Fact]
+        public async void Console_WriteLine_Has_Warning()
+        {
+            const string Source = @"
+using System;
+
+class TestClass 
+{
+    void TestMethod() {
+        Console.WriteLine(""Hello, World"");
+    }
+}";
+
+            await SpectreAnalyzerVerifier<UseSpectreInsteadOfSystemConsoleAnalyzer>
+                .VerifyAnalyzerAsync(Source, _expectedDiagnostics.WithLocation(7, 9))
+                .ConfigureAwait(false);
+        }
+    }
+}