JRuby/TruffleRuby Support

### Is your feature request related to a problem? Please describe.

Follow-up issue for https://github.com/fluent/fluentd/issues/317

The default Ruby interpreter MRI makes use of a GIL, which limits parallel execution to only a single thread. Especially in high-load scenarios, e.g. when FluentD is used as a log aggregator, the single-threaded execution becomes a bottleneck. To circumvent this issue, it is possible to either use multiple FluentD instances or to use the multi-worker feature of Fluentd. Using multiple instances of Fluentd often even is desired to allow horizontal scalability, but requires an effective load-balancing solution and results in higher costs, since each instance must be managed. The multi-worker feature solves these issues, but has a number of other problems: It was reported that the workload is unevenly distributed between workers, resulting in poor resource utilization (https://github.com/fluent/fluentd/issues/3346). In addition, the multi-worker feature makes use of processes and interprocess communication, which is much slower compared to multiple kernel threads in the same process.

Therefore, it would be great to use a interpreter without GIL, to boost performance and lower cost. Unfortunately, JRuby and TruffleRuby are currently not able to run Fluentd. In case of JRuby, the FluentD dependency `yajl-ruby` is not supported, since it doesn't provide a native Java extension. Truffleruby on the other hand is missing some functions (e.g. `IO#send_io`, `IO#recv_io`).

### Describe the solution you'd like

Adapt Fluentd to allow usage of JRuby/TruffleRuby or contribute the missing functions to the other projects.

### Describe alternatives you've considered

Implement Ractor based parallelism in serverengine (https://github.com/treasure-data/serverengine/issues/107), which should also result in a performance improvement.

### Additional context

_No response_