editor: Ensure minimap is shown when show_minimap is toggled to true (#30326)

Follow-up of #30285

This PR ensures the action added in the linked PR also works when the
user does not have the minimap enabled via settings. Currently, the
toggle only works when the user has already enabled the minimap in their
settings.

This happens because in


https://github.com/zed-industries/zed/blob/b4fbb9bc085733d2f771cd440ff57305cf6eebeb/crates/editor/src/element.rs#L7160-L7164

as well as


https://github.com/zed-industries/zed/blob/b4fbb9bc085733d2f771cd440ff57305cf6eebeb/crates/editor/src/element.rs#L1542

we check for the user configuration before reserving space for the
minimap as well as layouting it and because in

https://github.com/zed-industries/zed/blob/b4fbb9bc085733d2f771cd440ff57305cf6eebeb/crates/editor/src/editor.rs#L16404

with


https://github.com/zed-industries/zed/blob/b4fbb9bc085733d2f771cd440ff57305cf6eebeb/crates/editor/src/editor_settings.rs#L132-L134

we would not even create a minimap when the user disabled it via their
settings.

---

This PR fixes this by ensuring a minimap is created on the toggle issue
as well as lifting some of the restrictions. Since we are always only
returning a minimap in


https://github.com/zed-industries/zed/blob/b4fbb9bc085733d2f771cd440ff57305cf6eebeb/crates/editor/src/editor.rs#L16443-L16445

when `show_minimap` is set to `true`, we can assume in the rendering
code that if a minimap is present, it should be layouted and rendered no
matter if `ShowMinimap` is currently set to `Never`. We can do this
since `show_minimap` always reflects the current user configuration, see


https://github.com/zed-industries/zed/blob/b4fbb9bc085733d2f771cd440ff57305cf6eebeb/crates/editor/src/editor.rs#L18163-L18164

I also removed the minimap deletion/recreation on the toggling of
`show_minimap`, since this is not really needed - once we have stored a
minimap editor within the editor, `show_minimap` is sufficient to ensure
that it is only shown when the user requests it. Notice that we still
will never create a minimap unless neccesary.

Lastly, I updated the `supports_minimap` check to account for the fact
that the minimap is currently disabled entirely for multibuffers.

--- 

One thing I ~~did not tackle here~~ tackled in the second commit is that
due to `show_minimap` now being exposed to the user, it is possible to
enable the minimap for all full mode editors, e.g. the agent text thread
editor

<img width="592" alt="grafik"
src="https://github.com/user-attachments/assets/5f6c0e8b-45f9-44e8-9625-9d51c1480f98"
/>

which should most likely not be possible when the minimap is
programmatically disabled.

Release Notes:

- N/A

crates/zed/src/zed/quick_action_bar.rs

@@ -105,7 +105,7 @@ impl Render for QuickActionBar {
         let show_edit_predictions = editor_value.edit_predictions_enabled();
         let edit_predictions_enabled_at_cursor =
             editor_value.edit_predictions_enabled_at_cursor(cx);
-        let supports_minimap = editor_value.supports_minimap();
+        let supports_minimap = editor_value.supports_minimap(cx);
         let minimap_enabled = supports_minimap && editor_value.minimap().is_some();
 
         let focus_handle = editor_value.focus_handle(cx);