[fix][client] Fix OpenTelemetryProducerInterceptor not executing due to eligible check

[hrzzzz]

Fixes #25584

Modifications

Make the org.apache.pulsar.client.impl.tracing.OpenTelemetryProducerInterceptor#eligible method always return true, and determine whether the message can be processed in org.apache.pulsar.client.impl.tracing.OpenTelemetryProducerInterceptor#beforeSend.

Verifying this change

• Make sure that the change passes the CI checks.

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

[hrzzzz]

@Technoboy- @lhotari @codelipenghui @poorbarcode Could you please review this PR? Thanks