coverage: Store expression data in function coverage info

Even though expression details are now stored in the info structure, we still
need to inject `ExpressionUsed` statements into MIR, because if one is missing
during codegen then we know that it was optimized out and we can remap all of
its associated code regions to zero.

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -145,8 +145,8 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
                 );
                 bx.instrprof_increment(fn_name, hash, num_counters, index);
             }
-            CoverageKind::Expression { id, lhs, op, rhs } => {
-                func_coverage.add_counter_expression(id, lhs, op, rhs);
+            CoverageKind::ExpressionUsed { id } => {
+                func_coverage.mark_expression_id_seen(id);
             }
         }
     }