[transactions] Throttle clients on certain error during handleInitProducerId

[yzang2019]

Motivation

Cherry pick datastax/starlight-for-kafka@152625d

Modifications

Add throttling for COORDINATOR_LOAD_IN_PROGRESS and CONCURRENT_TRANSACTIONS during handleInitProducerId

Verifying this change

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This change is a trivial rework / code cleanup without any test coverage.

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[github-actions]

@yzang2019:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)

[github-actions]

@yzang2019:Thanks for providing doc info!

[Demogorgon314]

This commit already contains in #1923

[yzang2019]

This commit already contains in #1923

Thanks! Let me close it