zstd compression: stop using the streaming feature

[daipom]

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