Rollup merge of #107146 - compiler-errors:unsizing-params, r=cjgillot

Make `unsizing_params_for_adt` into a query

Addresses a FIXME in confirmation.

r? ``@ghost``

compiler/rustc_middle/src/query/mod.rs

@@ -183,6 +183,15 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    query unsizing_params_for_adt(key: DefId) -> rustc_index::bit_set::BitSet<u32>
+    {
+        arena_cache
+        desc { |tcx|
+            "determining what parameters of `{}` can participate in unsizing",
+            tcx.def_path_str(key),
+        }
+    }
+
     query analysis(key: ()) -> Result<(), ErrorGuaranteed> {
         eval_always
         desc { "running analysis passes on this crate" }