fix: Application.ExecutablePath returns dll instead of exe (#2801)

In .NET artifacts are DLLs even for executable projects. With some automagic
they get bundled into executables.
However `Assembly.GetEntryAssembly()` always returns the dll instead of the exe.

Following the guidance from the Runtime team retrieve the path to the
executable via `GetModuleFileNameW` call.

Resolves #1143

(cherry picked from commit 2af3af9)

src/System.Windows.Forms/src/System/Windows/Forms/Application.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
@@ -340,26 +340,8 @@ public static string ExecutablePath
             {
                 if (executablePath == null)
                 {
-                    Assembly asm = Assembly.GetEntryAssembly();
-                    if (asm == null)
-                    {
-                        StringBuilder sb = UnsafeNativeMethods.GetModuleFileNameLongPath(NativeMethods.NullHandleRef);
-                        executablePath = Path.GetFullPath(sb.ToString());
-                    }
-                    else
-                    {
-                        string cb = asm.CodeBase;
-                        Uri codeBase = new Uri(cb);
-                        if (codeBase.IsFile)
-                        {
-                            executablePath = codeBase.LocalPath + Uri.UnescapeDataString(codeBase.Fragment);
-                            ;
-                        }
-                        else
-                        {
-                            executablePath = codeBase.ToString();
-                        }
-                    }
+                    StringBuilder sb = UnsafeNativeMethods.GetModuleFileNameLongPath(NativeMethods.NullHandleRef);
+                    executablePath = Path.GetFullPath(sb.ToString());
                 }
 
                 return executablePath;