Unfortunately, the NSMenu-based bookmarks implementation cannot support
context menus within arbitrary folders. The NSMenu consumes the right-
click events during its own menu tracking, and we are not able to see
those events from our interface.
This patch replaces the NSMenu for folders with a custom NSPopup. This
implementation makes it much easier to handle context menus.
On macOS Tahoe, it is now recommended to show menu item icons. We use
system symbols for this now. Symbols do not have constant variable names
and must be found via the SF Symbols app.
The symbols chosen here were to match Safari as close as possible.
We currently duplicate a lot of code to handle application/context menus
and actions. The goal here is to hold the data for the menus and actions
in LibWebView. Each UI will then be able to generate menus from the data
on-the-fly.
The structures added here are meant to support generic and checkable
actions, action groups, submenus, etc.
