Fix ServiceController name population perf (dotnet/corefx#32072)

* Fix ServiceController name population perf

* Split tests

* Remove dead field

* Remove new use of DangerousGetHandle

* SafeHandle all the things!

* VSB #1

* VSB dotnet#2

* Fix GLE

* Initialize machineName in ctor

* Test for empty name ex

* Null names

* Inadvertent edit

* Unix build

* Move interop into class

* Reverse SafeHandle for HAllocGlobal

* Fix tests

* Disable test for NETFX

* CR feedback

* Pattern matching on VSB

* Direct call

* typo

Signed-off-by: dotnet-bot <dotnet-bot@microsoft.com>

src/System.Private.CoreLib/shared/System/Text/ValueStringBuilder.cs

@@ -48,11 +48,22 @@ public void EnsureCapacity(int capacity)
                 Grow(capacity - _chars.Length);
         }
 
+        /// <summary>
+        /// Get a pinnable reference to the builder.
+        /// Does not ensure there is a null char after <see cref="Length"/>
+        /// This overload is pattern matched in the C# 7.3+ compiler so you can omit
+        /// the explicit method call, and write eg "fixed (char* c = builder)"
+        /// </summary>
+        public ref char GetPinnableReference()
+        {
+            return ref MemoryMarshal.GetReference(_chars);
+        }
+
         /// <summary>
         /// Get a pinnable reference to the builder.
         /// </summary>
         /// <param name="terminate">Ensures that the builder has a null char after <see cref="Length"/></param>
-        public ref char GetPinnableReference(bool terminate = false)
+        public ref char GetPinnableReference(bool terminate)
         {
             if (terminate)
             {