zstd compression: stop using the streaming feature

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

The streaming feature (`Zstd::StreamWriter` and `Zstd::StreamReader`) of zstd-ruby is experimental.

* https://github.com/SpringMT/zstd-ruby?tab=readme-ov-file#stream-writer-and-reader-wrapper

Actually, there was a bug.
Although the critical bug has been resolved, some strange behavior is still being reported.

* https://github.com/SpringMT/zstd-ruby/issues/112
* https://github.com/SpringMT/zstd-ruby/issues/112#issuecomment-3339642856

We considered that we may not need to use the streaming feature.

* https://github.com/fluent/fluentd/pull/5094#issuecomment-3338027997

It would be better to stop using the streaming feature if it is unnecessary.

### Describe the solution you'd like

https://github.com/fluent/fluentd/pull/5094#issuecomment-3338027997

### Describe alternatives you've considered

None.

### Additional context

_No response_