Switch from Vec<InlayKind> to object with props

- Instead of a single object type, use several individual nested types
  to allow toggling from the settings GUI
- Remove unused struct definitions
- Install and test that the toggles work

crates/rust-analyzer/src/main_loop/handlers.rs

@@ -997,7 +997,7 @@ pub fn handle_inlay_hints(
     let analysis = world.analysis();
     let line_index = analysis.file_line_index(file_id)?;
     Ok(analysis
-        .inlay_hints(file_id, &world.options.inlay_hint_opts)?
+        .inlay_hints(file_id, &world.options.inlay_hints)?
         .into_iter()
         .map(|api_type| InlayHint {
             label: api_type.label.to_string(),