Add retry logic for webhooks

[tomach]

Summary of changes

Improve the robustness of webhooks by introducing a retry logic with exponential backoff.

Changes:

• Retries webhook requests on transient HTTP errors (502, 503, 504) and connection failures
• Limits retries to a fixed number of attempts with exponential backoff
• Disables retries for health check webhooks, as they are done every minute

Checklist

• Link to issue this PR refers to: https://github.com/crate/cloud/issues/2818
• Relevant changes are reflected in CHANGES.rst
• Added or changed code is covered by tests
• Documentation has been updated if necessary
• Changed code does not contain any breaking changes (or this is a major version change)

[plaharanne]

👍