Merge #2179

2179: Use HirDatabase to compute `is_deprecated` r=matklad a=martskins

This PR fixes #2167 by introducing `attributes_query` and adding `fn attrs(&self, def: crate::AttrDef) -> Option<Arc<[Attr]>>;`  to the `DefDatabase` trait.

I'm a little concerned about the two spots in `attributes_query` where code is repeated, but I couldn't figure out a way to avoid that, so.. I welcome suggestions 😄 



Co-authored-by: Martin Asquino <martin.asquino@gmail.com>

crates/ra_hir/src/code_model.rs

@@ -2,6 +2,7 @@
 
 pub(crate) mod src;
 pub(crate) mod docs;
+pub(crate) mod attrs;
 
 use std::sync::Arc;