feat(promotion): add pollInterval configuration

[mrfelton]

I'm mostly just throwing this PR together to help facilitate a question related to the discussion in #4969 - not expecting this to be properly reviewed or merged etc. So take it for what it is.

I'm not familiar with the codebase at all, but from what I gather, returning RetryAfter from these steps should be enough to prompt a more timely polling?

@krancour - just curious if an approach like this would work in principle? Or if this is more or less aligned with your vision of how to solve for the polling scenarios.

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This pull request introduces support for a configurable polling interval (pollInterval) for both the Git PR waiter and HTTP requester promotion steps. This allows users to specify how frequently these steps should poll for status updates, improving flexibility and responsiveness. If the interval is not specified or is invalid, the system falls back to the default 5-minute requeue interval. The changes include updates to configuration schemas, code logic, and documentation.

Polling interval support for promotion steps:

• Added a new pollInterval field to both GitWaitForPRConfig and HTTPConfig structs, allowing users to specify a custom polling interval. [1] [2]
• Updated JSON schemas (git-wait-for-pr-config.json, http-config.json) to validate and document the new pollInterval field, including accepted formats and default behavior. [1] [2]
• Modified the logic in git_pr_waiter.go and http_requester.go to parse the pollInterval value and set the RetryAfter field accordingly. If the interval is invalid, a warning is logged and the default is used. [1] [2] [3]

Documentation updates:

• Updated user guide reference docs for both the Git PR waiter and HTTP requester steps to describe the new pollInterval option and its default behavior. [1] [2]

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[aslafy-z]

I'm also really interested into this change. I need the pr waiter to pick up changes faster!

[krancour]

With apologies, I'm closing all PRs related to #5313 until adequate discussion and due diligence have been performed.

See #4969 (comment)