[macOS] Fix popup topmost

[maxkatz6]

What is the current behavior?

Right now macOS implementation of popup has two problems with topmost:

1. Initial Popup.Topmost=false value acts like it's "true". I.e. popup is always topmost.
2. Setting Popup.Topmost=true changes window type from NSPopUpMenuWindowLevel to NSFloatingWindowLevel (not really an issue, I think, but unwanted)
3. Setting Popup.Topmost=false after it was set to true once, will reset it to NSNormalWindowLevel. It will cause popup to go behind of parent window.

Screen.Recording.2021-12-05.at.11.03.09.PM.mov

What is the updated/expected behavior with this PR?

1. Topmost value doesn't affects NSPopUpMenuWindowLevel type
2. When window is deactivated, popup is hiding, so it's not staying top most

NOTE
This PR introduces another issue. Now when parent loses focus, but still visible on screen, popup will hide anyway. See the video. Workaround is easy - set Topmost=true, so this popup will act as it was before this PR. So I don't think it block this PR from merging. But ideally this should be fixed as well, preferably by somebody who is more familiar with macos backend.

Screen.Recording.2021-12-05.at.11.10.44.PM.mov

Fixed issues

Partially fixes #4630 and #4227 (only macos)

[jmacato]

Closing due to inactivity, @maxkatz6 just reopen this if you're gonna work on this again