Reuses bytes.Reader and value stack in func validation (#1340)

Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>

internal/wasm/module_test.go

@@ -465,7 +465,7 @@ func TestModule_validateFunctions(t *testing.T) {
 		m := Module{}
 		err := m.validateFunctions(api.CoreFeaturesV1, []uint32{1, 2, 3, 4}, nil, nil, nil, 3)
 		require.Error(t, err)
-		require.EqualError(t, err, "too many functions in a module")
+		require.EqualError(t, err, "too many functions (4) in a module")
 	})
 	t.Run("function, but no code", func(t *testing.T) {
 		m := Module{