Show "Bring All to Front" only on macOS

[luixxiul]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Fixes #3664
If there is a linux distribution where it works, please let me know. Thanks.

Auditors: @bbondy

Test Plan:

1. Make sure "Bring All to Front" appears in the menu "Window" on macOS
2. Make sure it does not appear in the menu on Windows

[bbondy]

I think it's only for macOS. Thanks.