elixir: Support describe, test, setup, setup_all in outlines (#19135)

Closes #9894 

Release Notes:

- N/A

### Before


![2024-10-12T204848@2x](https://github.com/user-attachments/assets/84b7f123-8845-4e6d-b1b1-444e54ea6599)

### After


![2024-10-12T204749@2x](https://github.com/user-attachments/assets/67fdcead-bad3-4967-9ac4-0b85f1da7bca)

extensions/elixir/languages/elixir/outline.scm

@@ -3,6 +3,16 @@
   (arguments (alias) @name)
   (#match? @context "^(defmodule|defprotocol)$")) @item
 
+(call
+  target: (identifier) @context
+  (arguments (_) @name)?
+  (#match? @context "^(setup|setup_all)$")) @item
+
+(call
+  target: (identifier) @context
+  (arguments (string) @name)
+  (#match? @context "^(describe|test)$")) @item
+
 (unary_operator
   operator: "@" @name
   operand: (call