Implement upload retries for reviewables and add user-friendly timeout error; update validation help

[FuzzkingCool]

While we don't use AYON reviews, its baked into the publishes so when I ran into numerous timeouts today, which almost always were fine the 2nd attempt to publish, I created this pull request.

Changelog Description

• Adds exponential backoff retries (3) when uploading reviewable files to AYON.
• Raises a clear, user-facing validation error on repeated timeouts with actionable help text.
• Updates validation help docs to guide users when review uploads fail.

Additional info

Retry policy: up to 3 attempts with backoff (2s, 4s, 8s). On exhaustion, raises PublishXmlValidationError with key="upload_timeout" and formatting data for file and error.

Testing notes:

Honestly not sure if you do not have a way to simulate the timeout. The timeouts were common today so I was able to test.

[FuzzkingCool]

I've revised integrate_review.py based on discussion so far.

[iLLiCiTiT]

Replaced by https://github.com/ynput/ayon-core/pull/1585