Add test case for append option without compression

[yaojingguo]

See #3569.

Which issue(s) this PR fixes:
Fixes #

What this PR does / why we need it:

Docs Changes:

Release Note:

[ashie]

As described in #3569 and https://bugs.ruby-lang.org/issues/18388, Ruby 2.7 and 3.0 on macOS have the issue.
Our CI with this test expectedly indicates it.
https://github.com/fluent/fluentd/runs/4602455215?check_suite_focus=true

Failure: test: append without compression(FileOutputTest)
/Users/runner/work/fluentd/fluentd/test/plugin/test_out_file.rb:440:in `check_result'
/Users/runner/work/fluentd/fluentd/test/plugin/test_out_file.rb:415:in `block in check_events_append'
/Users/runner/work/fluentd/fluentd/test/plugin/test_out_file.rb:408:in `upto'
/Users/runner/work/fluentd/fluentd/test/plugin/test_out_file.rb:408:in `check_events_append'
/Users/runner/work/fluentd/fluentd/test/plugin/test_out_file.rb:589:in `block in <class:FileOutputTest>'
     586:   end
     587: 
     588:   test 'append without compression' do
  => 589:     check_events_append(false)
     590:   end
     591: 
     592:   test 'append when JST' do
<"2011-01-02T13:14:15Z\ttest\t{\"a\":1}\n" +
"2011-01-02T13:14:15Z\ttest\t{\"a\":2}\n" +
"2011-01-02T13:14:15Z\ttest\t{\"a\":1}\n" +
"2011-01-02T13:14:15Z\ttest\t{\"a\":2}\n">(UTF-8) expected but was
<"2011-01-02T13:14:15Z\ttest\t{\"a\":1}\n" +
"2011-01-02T13:14:15Z\ttest\t{\"a\":2}\n">(ASCII-8BIT)

diff:
- 2011-01-02T13:14:15Z	test	{"a":1}
- 2011-01-02T13:14:15Z	test	{"a":2}
  2011-01-02T13:14:15Z	test	{"a":1}
  2011-01-02T13:14:15Z	test	{"a":2}
  
? Encoding: UTF  -8   
?           ASCII  BIT
?           ???  +++

[ashie]

I removed check_events_append method, use data driven test instead to make easy to read.

[ashie]

The test should be merged with #3579, so I close this one.
Thanks for your contribution!