Add assertions for matches that used to use analyze_branch (#5733)

Following up from #5730, add debug assertions to ensure that new branch instructions don't slip through matches that used to use analyze_branch.

cranelift/codegen/src/verifier/mod.rs

@@ -1358,7 +1358,7 @@ impl<'a> Verifier<'a> {
                     }
                 }
             }
-            _ => {}
+            inst => debug_assert!(!inst.opcode().is_branch()),
         }
 
         match self.func.dfg.insts[inst].analyze_call(&self.func.dfg.value_lists) {