Extract Elixir extension (#10948)

This PR extracts Elixir support into an extension and removes the
built-in Elixir support from Zed.

As part of this, [Lexical](https://github.com/lexical-lsp/lexical) has
been added as an available language server for Elixir.

Since the Elixir extension provides three different language servers,
you'll need to use the `language_servers` setting to select the one you
want to use:

#### Elixir LS

```json
{
  "languages": {
    "Elixir": {
      "language_servers": [ "elixir-ls", "!next-ls", "!lexical", "..."]
    }
  }
}
```

#### Next LS

```json
{
  "languages": {
    "Elixir": {
      "language_servers": [ "next-ls", "!elixir-ls", "!lexical", "..."]
    }
  }
}
```

#### Lexical

```json
{
  "languages": {
    "Elixir": {
      "language_servers": [ "lexical", "!elixir-ls", "!next-ls", "..."]
    }
  }
}
```

These can either go in your user settings or your project settings.

Release Notes:

- Removed built-in support for Elixir, in favor of making it available
as an extension.

crates/languages/src/lib.rs

@@ -3,22 +3,16 @@ use gpui::{AppContext, BorrowAppContext};
 pub use language::*;
 use node_runtime::NodeRuntime;
 use rust_embed::RustEmbed;
-use settings::{Settings, SettingsStore};
+use settings::SettingsStore;
 use smol::stream::StreamExt;
 use std::{str, sync::Arc};
 use util::{asset_str, ResultExt};
 
-use crate::{
-    bash::bash_task_context, elixir::elixir_task_context, python::python_task_context,
-    rust::RustContextProvider,
-};
-
-use self::elixir::ElixirSettings;
+use crate::{bash::bash_task_context, python::python_task_context, rust::RustContextProvider};
 
 mod bash;
 mod c;
 mod css;
-mod elixir;
 mod go;
 mod json;
 mod python;
@@ -47,14 +41,11 @@ pub fn init(
     node_runtime: Arc<dyn NodeRuntime>,
     cx: &mut AppContext,
 ) {
-    ElixirSettings::register(cx);
-
     languages.register_native_grammars([
         ("bash", tree_sitter_bash::language()),
         ("c", tree_sitter_c::language()),
         ("cpp", tree_sitter_cpp::language()),
         ("css", tree_sitter_css::language()),
-        ("elixir", tree_sitter_elixir::language()),
         (
             "embedded_template",
             tree_sitter_embedded_template::language(),
@@ -62,7 +53,6 @@ pub fn init(
         ("go", tree_sitter_go::language()),
         ("gomod", tree_sitter_gomod::language()),
         ("gowork", tree_sitter_gowork::language()),
-        ("heex", tree_sitter_heex::language()),
         ("jsdoc", tree_sitter_jsdoc::language()),
         ("json", tree_sitter_json::language()),
         ("markdown", tree_sitter_markdown::language()),
@@ -131,46 +121,9 @@ pub fn init(
             Arc::new(tailwind::TailwindLspAdapter::new(node_runtime.clone())),
         ]
     );
-
-    match &ElixirSettings::get(None, cx).lsp {
-        elixir::ElixirLspSetting::ElixirLs => {
-            language!(
-                "elixir",
-                vec![
-                    Arc::new(elixir::ElixirLspAdapter),
-                    Arc::new(tailwind::TailwindLspAdapter::new(node_runtime.clone())),
-                ],
-                elixir_task_context()
-            );
-        }
-        elixir::ElixirLspSetting::NextLs => {
-            language!(
-                "elixir",
-                vec![Arc::new(elixir::NextLspAdapter)],
-                elixir_task_context()
-            );
-        }
-        elixir::ElixirLspSetting::Local { path, arguments } => {
-            language!(
-                "elixir",
-                vec![Arc::new(elixir::LocalLspAdapter {
-                    path: path.clone(),
-                    arguments: arguments.clone(),
-                })],
-                elixir_task_context()
-            );
-        }
-    }
     language!("go", vec![Arc::new(go::GoLspAdapter)]);
     language!("gomod");
     language!("gowork");
-    language!(
-        "heex",
-        vec![
-            Arc::new(elixir::ElixirLspAdapter),
-            Arc::new(tailwind::TailwindLspAdapter::new(node_runtime.clone())),
-        ]
-    );
     language!(
         "json",
         vec![Arc::new(json::JsonLspAdapter::new(
@@ -232,6 +185,7 @@ pub fn init(
 
     let tailwind_languages = [
         "Astro",
+        "HEEX",
         "HTML",
         "PHP",
         "Svelte",