Auto merge of #80692 - Aaron1011:feature/query-result-debug, r=estebank

Enforce that query results implement Debug

Currently, we require that query keys implement `Debug`, but we do not do the same for query values. This can make incremental compilation bugs difficult to debug - there isn't a good place to print out the result loaded from disk.

This PR adds `Debug` bounds to several query-related functions, allowing us to debug-print the query value when an 'unstable fingerprint' error occurs. This required adding `#[derive(Debug)]` to a fairly large number of types - hopefully, this doesn't have much of an impact on compiler bootstrapping times.

compiler/rustc_data_structures/src/stable_hasher.rs

@@ -552,6 +552,7 @@ pub fn hash_stable_hashmap<HCX, K, V, R, SK, F>(
 
 /// A vector container that makes sure that its items are hashed in a stable
 /// order.
+#[derive(Debug)]
 pub struct StableVec<T>(Vec<T>);
 
 impl<T> StableVec<T> {

compiler/rustc_data_structures/src/steal.rs

@@ -21,6 +21,7 @@ use crate::sync::{MappedReadGuard, ReadGuard, RwLock};
 /// -- once the value is stolen -- it will never be read from again.
 //
 // FIXME(#41710): what is the best way to model linear queries?
+#[derive(Debug)]
 pub struct Steal<T> {
     value: RwLock<Option<T>>,
 }