Update keymap context binding behavior of > and ! (#34664)

Now ! means "no ancestors matches this", and > means "any descendent"
not "any child".

Updates #34570

Co-authored-by: Ben Kunkle <ben@zed.dev>

Release Notes:

- *Breaking change*. The context predicates in the keymap file now
handle ! and > differently. Before this change ! meant "this node does
not match", now it means "none of these nodes match". Before this change
> meant "child of", now it means "descendent of". We do not expect these
changes to break many keymaps, but they may cause subtle changes for
complex context queries.

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>

crates/settings_ui/src/keybindings.rs

@@ -3008,7 +3008,7 @@ fn collect_contexts_from_assets() -> Vec<SharedString> {
                         contexts.insert(ident_a);
                         contexts.insert(ident_b);
                     }
-                    gpui::KeyBindingContextPredicate::Child(ctx_a, ctx_b) => {
+                    gpui::KeyBindingContextPredicate::Descendant(ctx_a, ctx_b) => {
                         queue.push(*ctx_a);
                         queue.push(*ctx_b);
                     }