Move test projects from src/ to tests/ (#11357)

* Update gitignore

* Move csproj

* Update project references

* Update solutions

* Update build scripts

* Tests used to share editorconfig with projects in src

* Fix broken tests.

* Stop copying around .editorconfig

merged root one with linting

* csharp_style_expression_bodied -> suggestion

* Move StyleCop rulesets to matching directories and update shared build properties

* Remove legacy build files, update NuGet.cofig and solution files

* Restore myget source

* Clean up .gitignore

* Update .gitignore

* Move new test classes to tests after merge

* Gitignore + nuget config

* Move new test

Co-authored-by: Ronald Barendse <ronald@barend.se>

tests/Umbraco.Tests.Common/Builders/Extensions/StringExtensions.cs

@@ -0,0 +1,23 @@
+// Copyright (c) Umbraco.
+// See LICENSE for more details.
+
+namespace Umbraco.Cms.Tests.Common.Builders.Extensions
+{
+    public static class StringExtensions
+    {
+        public static string ToCamelCase(this string s)
+        {
+            if (string.IsNullOrWhiteSpace(s))
+            {
+                return string.Empty;
+            }
+
+            if (s.Length == 1)
+            {
+                return s.ToLowerInvariant();
+            }
+
+            return char.ToLowerInvariant(s[0]) + s.Substring(1);
+        }
+    }
+}