inline completions: Add action to toggle inline completions (#16947)

This adds a new action: `editor: toggle inline completions`.

It allows users to toggle inline completions on/off for the current
buffer.

That toggling is not persistent and when the editor is closed, it's
gone.

That makes it easy to disable inline completions for a single text
buffer, for example, even if you want them on for other buffers.

When toggling on/off, the toggling also overwrites any language
settings. So if you have inline completions disabled for Go buffers,
toggling them on takes precedence over those settings.


Release Notes:

- Added a new editor action to allow toggling inline completions
(Copilot, Supermaven) on and off for the current buffer, taking
precedence over any settings.

Co-authored-by: Antonio <antonio@zed.dev>

crates/feedback/src/feedback_modal.rs

@@ -186,7 +186,7 @@ impl FeedbackModal {
             );
             editor.set_show_gutter(false, cx);
             editor.set_show_indent_guides(false, cx);
-            editor.set_show_inline_completions(false);
+            editor.set_show_inline_completions(Some(false), cx);
             editor.set_vertical_scroll_margin(5, cx);
             editor.set_use_modal_editing(false);
             editor