WebAssembly: fix execution context for methods that require Window interface

[x1unix]

Our playground uses special proxy object to inject/customize global scope of Go's WebAssembly bridge (wasm_exec.js) by wrapping globalThis with proxy object.

Some window calls, like window.alert require that execution context object should be window.

When proxy object passed instead, occurs an error:

TypeError: 'alert' called on an object that does not implement interface Window

Prototype swap by using setPrototypeOf also doesn't work.

This PR adds method owner check during method call as a workaround, which replaces proxy object with original window during call on any window member method (like alert()).