Add the ability to customize available models for OpenAI-compatible services (#13276)

Closes #11984, closes #11075.

Release Notes:

- Added the ability to customize available models for OpenAI-compatible
services ([#11984](https://github.com/zed-industries/zed/issues/11984))
([#11075](https://github.com/zed-industries/zed/issues/11075)).


![image](https://github.com/zed-industries/zed/assets/32017007/01057e7b-1f21-49ad-a3ad-abc5282ffaf0)

crates/assistant/src/inline_assistant.rs

@@ -1298,7 +1298,8 @@ impl Render for PromptEditor {
                         PopoverMenu::new("model-switcher")
                             .menu(move |cx| {
                                 ContextMenu::build(cx, |mut menu, cx| {
-                                    for model in CompletionProvider::global(cx).available_models() {
+                                    for model in CompletionProvider::global(cx).available_models(cx)
+                                    {
                                         menu = menu.custom_entry(
                                             {
                                                 let model = model.clone();