Add setting for hover delay (#22006)

This PR adds a new `hover_popover_delay` setting that allows the user to
specify how long to wait before showing informational hover boxes. It
defaults to the existing delay.

Release Notes:

- Added a setting to control the delay for informational hover boxes

assets/settings/default.json

@@ -101,6 +101,8 @@
   // Whether to show the informational hover box when moving the mouse
   // over symbols in the editor.
   "hover_popover_enabled": true,
+  // Time to wait before showing the informational hover box
+  "hover_popover_delay": 350,
   // Whether to confirm before quitting Zed.
   "confirm_quit": false,
   // Whether to restore last closed project when fresh Zed instance is opened.