add try_produce and rustdoc guidance for Producer<T>

[josemanuel657]

add try_produce and rustdoc guidance for Producer

Description

Adds Producer::try_produce, a non-blocking fallible push for callers that need a meaningful response to backpressure. Returns the value back via TryProduceError::Full if a bounded buffer is at capacity, or TryProduceError::Closed if the record is shutting down — instead of silently overwriting as produce does.

Extends the internal WriteHandle trait with a default try_push that delegates to push and returns Ok(()), so all existing buffer implementations require no changes. Bounded/non-overwriting buffers override it to return the appropriate error variant.

Also updates the rustdoc on both produce and try_produce with the suggested phrasing and no_run examples so callers can pick the right method without reading the implementation.

Related Issue

• Closes [FEAT] Non-blocking fallible try_produce for bounded / non-overwriting buffers #116

Checklist

• I have read the CONTRIBUTING.md document.
• My code follows the project's coding standards.
• I have added tests to cover my changes.
• All new and existing tests passed (make check).
• I have updated the documentation accordingly.