feat: add advanced retry policy

[Apollorion]

Description of the change

This adds an "advanced retry policy" that will allow users to configure a retry policy that retries more than once.

Users can set the max_retries default to the absolute maximum the policy will allow. By default, the policy will retry up to max_retries but users can also set the spacelift_retry:<number> label on a stack and it will then retry up to that number or up to the policies max_retries whichever is less.

If the run succeeds, it does not retry:

If the tracked run fails, it retries 3 times by default:

If the stack has the spacelift_retry:2 label on it, it will only retry twice:

Checklist

Please make sure that the proposed change checks all the boxes below before requesting a review:

• Each new policy has corresponding tests.
• All the tests pass.
• The pull request is opened against the main branch.
• The pull request is no longer marked as a draft.
• You agree to license your contribution under the MIT license to Spacelift (not required for Spacelift employees).

If the proposed change is ready to be merged, please request a review from @spacelift-io/solutions-engineering. Someone will review and merge the pull request.

Spacelift employees should request reviews from the relevant engineers and are allowed to merge pull requests after they got at least one approval.

Thank you for your contribution! 🙇