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.rs

@@ -177,7 +177,7 @@ pub fn main_loop(
                     .and_then(|it| it.folding_range.as_ref())
                     .and_then(|it| it.line_folding_only)
                     .unwrap_or(false),
-                inlay_hint_opts: config.inlay_hint_opts,
+                inlay_hints: config.inlay_hints,
                 cargo_watch: CheckOptions {
                     enable: config.cargo_watch_enable,
                     args: config.cargo_watch_args,