[ty] Default ty.inlayHints.* server settings to true (#19910)

## Summary

This PR changes the default of `ty.inlayHints.*` settings to `true`.

I somehow missed this in my initial PR.

This is marked as `internal` because it's not yet released.

crates/ty_server/src/session/options.rs

@@ -243,8 +243,8 @@ struct InlayHintOptions {
 impl InlayHintOptions {
     fn into_settings(self) -> InlayHintSettings {
         InlayHintSettings {
-            variable_types: self.variable_types.unwrap_or_default(),
-            function_argument_names: self.function_argument_names.unwrap_or_default(),
+            variable_types: self.variable_types.unwrap_or(true),
+            function_argument_names: self.function_argument_names.unwrap_or(true),
         }
     }
 }

crates/ty_server/tests/e2e/inlay_hints.rs

@@ -5,6 +5,60 @@ use ty_server::ClientOptions;
 
 use crate::TestServerBuilder;
 
+/// Tests that the default value of inlay hints settings is correct i.e., they're all enabled
+/// by default.
+#[test]
+fn default_inlay_hints() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "\
+x = 1
+
+def foo(a: int) -> int:
+    return a + 1
+
+foo(1)
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(ClientOptions::default())
+        .with_workspace(workspace_root, None)?
+        .with_file(foo, foo_content)?
+        .enable_inlay_hints(true)
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    server.open_text_document(foo, &foo_content, 1);
+    let _ = server.await_notification::<PublishDiagnostics>()?;
+
+    let hints = server
+        .inlay_hints_request(foo, Range::new(Position::new(0, 0), Position::new(6, 0)))?
+        .unwrap();
+
+    insta::assert_json_snapshot!(hints, @r#"
+    [
+      {
+        "position": {
+          "line": 0,
+          "character": 1
+        },
+        "label": ": Literal[1]",
+        "kind": 1
+      },
+      {
+        "position": {
+          "line": 5,
+          "character": 4
+        },
+        "label": "a=",
+        "kind": 1
+      }
+    ]
+    "#);
+
+    Ok(())
+}
+
 /// Tests that disabling variable types inlay hints works correctly.
 #[test]
 fn variable_inlay_hints_disabled() -> Result<()> {