Add tests to improve code coverage (#187)

* DbColumn and ReliableConnection tests

* More retry connection tests

* More tests

* Fix broken peek definition integration tests

* Fix test bug

* Add a couple batch tests

* Add some more tests

* More tests for code coverage.

* Validation and Diagnostic tests

* A few more tests

* A few mote test changes.

* Update file path tests to run on Windows only

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Contracts/DbColumnWrapper.cs

@@ -19,7 +19,7 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts
         /// <summary>
         /// All types supported by the server, stored as a hash set to provide O(1) lookup
         /// </summary>
-        private static readonly HashSet<string> AllServerDataTypes = new HashSet<string>
+        internal static readonly HashSet<string> AllServerDataTypes = new HashSet<string>
         {
             "bigint",
             "binary",