feat: Add support to enable backoff when rate limited by the Github API

[andrewhibbert]

Adds support to backoff when a rate limit error occurs as per handle rate limit errors appropriately:

• If the retry-after response header is present, you should not retry your request until after that many seconds has elapsed.
• If the x-ratelimit-remaining header is 0, you should not make another request until after the time specified by the x-ratelimit-reset header. The x-ratelimit-reset header is in UTC epoch seconds.

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Fixes #6643

Relates to kedacore/keda-docs#1557

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