PodProtector-level rejection count metrics

[SOF3]

• Add a .status.rejectionHistory field in the PodProtector CRD that stores the last N rejections (or rejection buckets). N may be configured through
• Expand the retrybatch adaptor to support two types of requests: admission attempt (the current type) and rejection log. Submit a rejection log request when an admission attempt is rejected. The rejection log request has no timeout, but it gets canceled when the rejection log cannot fit into the latest PodProtector status (e.g. more than N rejections (or rejection buckets) were created afterwards, or PodProtector is deleted, or other errors).
• Aggregate the rejection history status in the past few minutes in generator/monitor. generator/observer/metrics can report this as a gauge metric (or a histogram metric where each rejection bucket is a histogram bucket) indicating the number of PodProtectors with rejections during the (last) rejection bucket.