Log state changes caused by webhook execution

What does this MR do and why?

See: #354126 (closed)

When enabling web_hooks_disable_failed we encountered frequent failures in gitlab-org and gitlab-com hooks due to hook receivers exceeding the timeout. These failures are legitimate (we document the timeout, and advise sub-second response times), but cause disruption of our systems, and lead to the disabling of the feature flag.

To gather information on the impact of this change, we should add logging to help analyse these changes.

The aim here is purely diagnostic.

How to set up and validate locally

1. Set up one or more hooks
2. Perform some actions (or use the 'test webhook' functionality on the webhooks page)
3. See the log messages in the logs

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.