[FLINK-29207][connector/pulsar] release-1.16 Fix Pulsar message eventTime may be incorrectly set to a negative number

[wenbingshen]

What is the purpose of the change

We'd better judge that the timestamp is greater than 0, we should skip setting eventTime when timestamp less than or equal to 0, otherwise the pulsar client will throw an exception.

Brief change log

check the timestamp is greater than 0

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[flinkbot]

CI report:

• 0f36bf0 UNKNOWN

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[wenbingshen]

ping @tisonkun PTAL, Thanks.