coverageinfo query needs to use the same MIR as codegen

I ran into an error trying to fix dead block coverage and realized the
`coverageinfo` query is getting a different MIR compared to the
codegenned MIR, which can sometimes be a problem during mapgen.

I changed that query to use the `InstandeDef` (which includes the
generic parameter substitutions, prosibly specific to const params)
instead of the `DefId` (without unknown/default const substitutions).

compiler/rustc_codegen_ssa/src/coverageinfo/map.rs

@@ -49,9 +49,9 @@ impl<'tcx> FunctionCoverage<'tcx> {
     }
 
     fn create(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>, is_used: bool) -> Self {
-        let coverageinfo = tcx.coverageinfo(instance.def_id());
+        let coverageinfo = tcx.coverageinfo(instance.def);
         debug!(
-            "FunctionCoverage::new(instance={:?}) has coverageinfo={:?}. is_used={}",
+            "FunctionCoverage::create(instance={:?}) has coverageinfo={:?}. is_used={}",
             instance, coverageinfo, is_used
         );
         Self {