Fix the type of table bounds in DummyEnvironment.

Also, fix the wasm testsuite harness to run the verifier with a
TargetIsa so that it catches problems like this.

lib/wasm/src/environ/dummy.rs

@@ -206,7 +206,7 @@ impl<'dummy_environment> FuncEnvironment for DummyFuncEnvironment<'dummy_environ
         let bound_gv = func.create_global_value(ir::GlobalValueData::Load {
             base: vmctx,
             offset: Offset32::new(0),
-            global_type: self.pointer_type(),
+            global_type: I32,
         });
 
         func.create_table(ir::TableData {