Fix crash when specifying a state_file in Ruby > 3.2.0

[rophy]

Issue: the method File.exists() is removed since Ruby 3.2.0, and thus using a state_file will crash newer fluentd versions.
See: https://stackoverflow.com/a/75353113

Note: I am not a ruby developer, I simply copied the original test file and added state_file to it to reproduce the error. Let me know if this is not sufficient as unit tests.

Error: test_message(SqlInputStateFileTest): NoMethodError: undefined method `exists?' for File:Class
/home/kasm-user/fluent-plugin-sql/lib/fluent/plugin/in_sql.rb:285:in `initialize'
/home/kasm-user/fluent-plugin-sql/lib/fluent/plugin/in_sql.rb:186:in `new'
/home/kasm-user/fluent-plugin-sql/lib/fluent/plugin/in_sql.rb:186:in `start'
/home/kasm-user/.rvm/gems/ruby-3.2.2/gems/fluentd-1.16.3/lib/fluent/test/driver/base.rb:120:in `instance_start'
/home/kasm-user/.rvm/gems/ruby-3.2.2/gems/fluentd-1.16.3/lib/fluent/test/driver/base.rb:78:in `run'
/home/kasm-user/.rvm/gems/ruby-3.2.2/gems/fluentd-1.16.3/lib/fluent/test/driver/base_owner.rb:130:in `run'
/home/kasm-user/fluent-plugin-sql/test/plugin/test_in_sql_with_state_file.rb:78:in `test_message'

[ashie]

Thanks for your contribution!
The fix itself seems good.
Could you follow DCO?: https://github.com/fluent/fluent-plugin-sql/pull/144/checks?check_run_id=22075217219

[rophy]

Thanks for your contribution! The fix itself seems good. Could you follow DCO?: https://github.com/fluent/fluent-plugin-sql/pull/144/checks?check_run_id=22075217219

done

[ashie]

Note: CI with Ruby head is currently broken like this: fluent/fluentd#4411
I'll tackle on it in another pull request.

[ashie]

Merged. Thanks!
I'll release a new version after fixing CI.

[ashie]

I've released it as v2.3.1.