Improved shader cache hash key to not cause collisions (MonoGame#8557)

Fix for the following issue
MonoGame#8555

I made the key used for the shader program cache use a value tuple so it
can avoid potential hash key collisions.

Also made use of `TryGetValue` so it only has to check the key in the
dictionary once.

Author: arosolino

MonoGame.Framework/Platform/Graphics/Shader/ShaderProgramCache.cs

@@ -37,7 +37,7 @@ public int GetUniformLocation(string name)
     /// </summary>
     internal class ShaderProgramCache : IDisposable
     {
-        private readonly Dictionary<int, ShaderProgram> _programCache = new Dictionary<int, ShaderProgram>();
+        private readonly Dictionary<ulong, ShaderProgram> _programCache = new Dictionary<ulong, ShaderProgram>();
         GraphicsDevice _graphicsDevice;
         bool disposed;
 
@@ -69,14 +69,16 @@ public ShaderProgram GetProgram(Shader vertexShader, Shader pixelShader)
             // buffers here as well.  This would allow us to optimize
             // setting uniforms to only when a constant buffer changes.
 
-            var key = vertexShader.HashKey | pixelShader.HashKey;
-            if (!_programCache.ContainsKey(key))
+            var key = ((ulong)(uint)vertexShader.HashKey << 32) | (uint)pixelShader.HashKey;
+    
+            if(!_programCache.TryGetValue(key, out var shaderProgram))
             {
                 // the key does not exist so we need to link the programs
-                _programCache.Add(key, Link(vertexShader, pixelShader));
+                shaderProgram = Link(vertexShader, pixelShader);
+                _programCache.Add(key, shaderProgram);
             }
 
-            return _programCache[key];
+            return shaderProgram;
         }
 
         private ShaderProgram Link(Shader vertexShader, Shader pixelShader)
@@ -141,4 +143,4 @@ protected virtual void Dispose(bool disposing)
     }
 }
 
-#endif // OPENGL
+#endif // OPENGL