Problem: High-priority state requests that fail with 404 keep being sorted first in the loading queue indefinitely. The retry counts grow (30, 370, 740+) but they're still treated as high priority, starving low-priority requests like the epoch 0 synchronizer.

Fix: In the priority sorting (epochcache.go:348-349), high-priority status is now conditional on retryCount <= 3.
After 3 failed attempts, the request is demoted to low priority, allowing other requests to be processed first.

• Added beaconStateHighPriorityRetryCount = 3 constant in requests.go:22
• Modified the highPriority condition in the sort comparator to include && retryCount <= beaconStateHighPriorityRetryCount

The existing "probably bad" threshold (beaconStateRetryCount = 10) still applies as a separate layer — requests with >10 retries are sorted last regardless.