[codex] stream AWS ELBv2 collector results

[antdewei]

Summary

• Change AWS ELBv2 collection from batch-then-push to streaming push per load balancer.
• Stream the standalone ELB Listener resource as listeners are discovered instead of collecting all listeners before sending.
• Add deterministic streaming regression tests that would fail if the collector waits for every load balancer before emitting the first result.
• Add ELBv2 progress logs for load-balancer pages, processed load balancers, listener count, listener errors, and collection duration.

Root cause

PR #114 added per-load-balancer DescribeListeners calls, but the AWS ELBv2 collector still built the entire region result set before sending anything to regionCh. In regions with many ALB/NLB resources, that left the framework consumer idle long enough to hit the hard-coded 30s timeout, close the channel, and drop the whole region.

Validation

• go test ./collector/elasticloadbalancing -run 'TestStreamELB' -count=1
• go test ./collector/elasticloadbalancing ./collector ./platform
• go test ./... in collector/aws
• git diff --check

[gemini-code-assist]

Code Review

This pull request refactors the AWS Elastic Load Balancing collector to use a more efficient iteration pattern. It introduces a forEachELB helper function to handle pagination and execute callbacks for each load balancer, replacing the previous method of collecting all items into a slice. The GetELBDetail and GetELBListenerDetail functions were updated to use this pattern, and an unused import was removed. I have no feedback to provide.