fix: message size two large

[pauldambra]

follow up to https://github.com/PostHog/posthog/pull/23268

the mocks in the capture tests made the MessageSizeTooLarge solution work in tests, but it doesn't work in practice, sad times

this PR:

• updates the mock so it throws at the right time
• keeps track of the event args that cause each kafka future
• so that if the future throws MessageSizeTooLarge
• we can replace some content and retry the kafka produce

metric in place ready at https://grafana.prod-us.posthog.dev/d/session-replay/session-replay?var-role=recordings-blob-ingestion&var-pod=$__all&var-partition=$__all&from=now-1h&to=now&timezone=utc&tab=queries&viewPanel=panel-74

this set of exception handlers is pretty ugly now but i don't want to spend time refactoring this till i've confirmed it has the desired effect in prod

[sentry-io[bot]]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: posthog/api/capture.py

Function	Unhandled Issue
get_event	UnicodeDecodeError: 'utf-16-le' codec can't decode bytes in position 21438-21439: illegal UTF-16 surrogate ... Event Count: 4

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[sentry-io[bot]]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ KafkaTimeoutError: KafkaTimeoutError: Timeout after waiting for 8.914257952999833 secs. /s/[#].* View Issue
• ‼️ KafkaTimeoutError: KafkaTimeoutError: Timeout after waiting for 10 secs. /s/[#].* View Issue
• ‼️ ClientError: An error occurred (AccessDenied) when calling the PutObject operation: Access Denied /s/[#].* View Issue

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