[NOGIL] Make Message class methods thread safe

[Ojasva Jain (ojasvajain)]

• Message class exposes getters and setters to five fields. On free threaded Python builds, calling setters and getters concurrently can cause use-after-free conditions and incorrect reference counts.

• This PR fixes this by acquiring a lock around code snippets where we want only one thread to run at a time (critical sections). The getters and setters have been refactored as part of this process. In Message_headers, an unrelated bug related to error not being handled is also fixed.

• For the five fields that have getters and setters, we have introduced five lock fields within the Message struct.

• Also contains a minor fix in Consumer_consume method.

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Checklist

• Contains customer facing changes? Including API/behavior changes
• Did you add sufficient unit test and/or integration test coverage for this PR?
  • If not, please explain why it is not required

References

JIRA:

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Open questions / Follow-ups

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[sonarqube-confluent]

Quality Gate failed

Failed conditions
5.9% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube

[Kaushik Raina (k-raina)]

Thanks for PR! Provided couple of comments

[Kaushik Raina (k-raina)]

Why are we not checking lock for "==" , "len()" etc?

[Kaushik Raina (k-raina)]

Can we expand more on test coverage, considering its change to message class? One thing i can thing of is memory leak test by counting refcount before and after?