fix(macos): fix race condition in wkwebview implementation of cookie fetching

[charrondev]

As I was implementing tauri-apps/tauri#12665 I noticed a completed hang of the application if cookies_for_url() was called multiple times in quick succession.

I'm no expect in rust or objc but my understanding of the code here is as follows:

• WKHTTPCookieStore.getAllCookies() takes a callback to receive the cookies.
• The interface we expose for fetching cookies is synchronous, so we need to loop and block for some period of time until we receive our results.
• Looping purely in rust won't actually do the work properly, since the objc runloop (running on another thread? (potentially?) needs to be told to progress.
• runUntilDate() didn't necessarily block until that date on the rust site of this operation.

In order to fix this I had to do a few things. Notably I had to do all of these things for the issue to go away consistently.

• Replace runUntilDate() with acceptInputForMode_beforeDate().
• Add some waiting in rust with by using recv_timeout() instead of try_recv

Now I'm sure there's something nasty under the hood causing this to happen, but I'm not really knowledgable enough to dive any deeper myself. I will say these changes fix the issue I was running into at the cost of an extra ms on my end.