Slightly refactor the dumping of HIR analysis data

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -22,8 +22,7 @@ mod constraints;
 /// Code to solve constraints and write out the results.
 mod solve;
 
-/// Code to write unit tests of variance.
-pub mod test;
+pub(crate) mod dump;
 
 /// Code for transforming variances.
 mod xform;