Add StringEscapingUtil that will be used in many places

src/Runner.Common/Util/StringEscapingUtil.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using GitHub.Runner.Sdk;
+using GitHub.Runner.Common;
+
+namespace GitHub.Runner.Common.Util
+{
+    public static class StrigEscapingUtil
+    {
+
+        private static readonly EscapeMapping[] _escapeDataMappings = new[]
+        {
+            new EscapeMapping(token: "\r", replacement: "%0D"),
+            new EscapeMapping(token: "\n", replacement: "%0A"),
+            new EscapeMapping(token: "%", replacement: "%25"),
+        };
+        public static string UnescapeData(string escaped)
+        {
+            if (string.IsNullOrEmpty(escaped))
+            {
+                return string.Empty;
+            }
+
+            string unescaped = escaped;
+            foreach (EscapeMapping mapping in _escapeDataMappings)
+            {
+                unescaped = unescaped.Replace(mapping.Replacement, mapping.Token);
+            }
+
+            return unescaped;
+        }
+        private sealed class EscapeMapping
+        {
+            public string Replacement { get; }
+            public string Token { get; }
+
+            public EscapeMapping(string token, string replacement)
+            {
+                ArgUtil.NotNullOrEmpty(token, nameof(token));
+                ArgUtil.NotNullOrEmpty(replacement, nameof(replacement));
+                Token = token;
+                Replacement = replacement;
+            }
+        }
+    }
+}