test: use `T.TempDir` to create temporary test directory

A testing cleanup.

This pull request replaces ioutil.TempDir with t.TempDir. We can use the T.TempDir function from the testing package to create temporary directory. The directory created by T.TempDir is automatically removed when the test and all its subtests complete.

Reference: https://pkg.go.dev/testing#T.TempDir

func TestFoo(t *testing.T) {
	// before
	tmpDir, err := ioutil.TempDir("", "")
	require.NoError(t, err)
	defer require.NoError(os.RemoveAll(tmpDir))

	// now
	tmpDir := t.TempDir()
}