Add LM Studio support to the Assistant (#23097)

#### Release Notes:

- Added support for [LM Studio](https://lmstudio.ai/) to the Assistant.

#### Quick demo:


https://github.com/user-attachments/assets/af58fc13-1abc-4898-9747-3511016da86a

#### Future enhancements:
- wire up tool calling (new in [LM Studio
0.3.6](https://lmstudio.ai/blog/lmstudio-v0.3.6))

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/language_model/src/role.rs

@@ -65,3 +65,13 @@ impl From<Role> for open_ai::Role {
         }
     }
 }
+
+impl From<Role> for lmstudio::Role {
+    fn from(val: Role) -> Self {
+        match val {
+            Role::User => lmstudio::Role::User,
+            Role::Assistant => lmstudio::Role::Assistant,
+            Role::System => lmstudio::Role::System,
+        }
+    }
+}