Fix WindowsBuilder executable path and enhance MSI linking error reporting

- Updated the path to the built executable to reflect changes in the output structure.
- Added calculation and display of total distribution size after build.
- Enhanced error reporting for the MSI linking process by capturing and printing stdout and stderr output.
- Updated WiX source file to include UI namespace for better compatibility.
- Removed unnecessary blank line in test_msi.py for cleaner code.

test_msi.py

@@ -8,7 +8,6 @@ sys.path.insert(0, str(Path(__file__).parent / "build" / "scripts"))
 
 from build_windows import WindowsBuilder
 
-
 if __name__ == "__main__":
     builder = WindowsBuilder()
     print("Creating MSI installer...")