Avoid unnecessary intermediate Version allocation (#4349)

`Version..ctor(string)` is implemented by calling `Version.Parse`, which
allocates an intermediate `Version` instance. Avoid the unnecessary
intermediate allocation by using `Version.Parse` directly.

src/System.Private.CoreLib/src/System/AppContextDefaultValues.cs

@@ -100,7 +100,7 @@ namespace System
                     {
                         value = value.Substring(1);
                     }
-                    Version realVersion = new Version(value);
+                    Version realVersion = Version.Parse(value);
                     // The version class will represent some unset values as -1 internally (instead of 0).
                     version = realVersion.Major * 10000;
                     if (realVersion.Minor > 0)

src/System.Private.CoreLib/src/System/Resources/ResourceManager.cs

@@ -748,7 +748,7 @@ namespace System.Resources
             Version ver;
             try
             {
-                ver = new Version(v);
+                ver = Version.Parse(v);
             }
             catch (ArgumentOutOfRangeException e)
             {