[feat i2g]setup e2e test for migration tool

[shuqz]

Description

• add a vanilla test case, which just compares generated gateway manifest with expected, supposed to be a fast fail is anything changes in migration tool logic
• add an end-to-end test for the lbc-migrate tool, validating the full ingress-to-gateway migration workflow: (i will add more test cases later but now it is one ingress manifest in builder.go)

1. creates an IngressGroup with 2 members (3 backend services, health checks, user tags)
   and verifies the ingress ALB serves traffic correctly
2. runs lbc-migrate --dry-run, applies generated manifests, verifies the
   gateway.k8s.aws/dry-run annotation prevents ALB creation, and validates the dry-run plan annotation
3. removes the dry-run annotation, waits for the gateway ALB to provision, then compares:
   - Listener ports and protocols
   - Listener rules compared in priority order; conditions within each rule matched by field type
   - Target group count and types
   - Tags on LB, listener rules, and target groups (user tags + migrated-from tag)
   - Default rule action types
4. Traffic verification — confirms identical HTTP responses from both ALBs
5. Resource count verification — asserts exactly the expected number of Gateway, HTTPRoute,
   LoadBalancerConfiguration, TargetGroupConfiguration, and ListenerRuleConfiguration resources are created

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested

------------------------------
ingress to gateway migration should produce expected gateway manifests from file input
/Users/shuqz/go/src/github.com/sigs.k8s.io/shuqz-aws-load-balancer-controller/test/e2e/ingress2gateway/migration_test.go:60
  STEP: setup sandbox namespace @ 05/14/26 16:34:47.636
  STEP: running lbc-migrate with --file input @ 05/14/26 16:34:49.482
  STEP: comparing output against golden file @ 05/14/26 16:34:49.608
  STEP: teardown sandbox namespace @ 05/14/26 16:34:49.613
• [8.152 seconds]
------------------------------
ingress to gateway migration should migrate an IngressGroup with multiple paths, tags, and health checks through dry-run and full cutover
/Users/shuqz/go/src/github.com/sigs.k8s.io/shuqz-aws-load-balancer-controller/test/e2e/ingress2gateway/migration_test.go:83
  STEP: setup sandbox namespace @ 05/14/26 16:34:55.788
  STEP: creating backend services @ 05/14/26 16:34:55.827
  STEP: creating IngressGroup (2 members) @ 05/14/26 16:34:58.143
  STEP: waiting for Ingress ALB to be provisioned @ 05/14/26 16:34:58.207
  {"level":"info","ts":1778801702.261599,"msg":"ingress DNS populated","dns":"k8s-e2emigi2ge2eaf00b-3ce3159a2f-1979745003.us-west-2.elb.amazonaws.com"}
  {"level":"info","ts":1778801702.478559,"msg":"waiting for ingress ALB to be available"}
  STEP: verifying traffic to ingress ALB @ 05/14/26 16:38:04.384
  {"level":"info","ts":1778801884.3848152,"msg":"waiting for LB DNS to be resolvable","dns":"k8s-e2emigi2ge2eaf00b-3ce3159a2f-1979745003.us-west-2.elb.amazonaws.com"}
  STEP: verifying dry-run-plan annotation on primary member only @ 05/14/26 16:38:04.506
  STEP: running lbc-migrate tool @ 05/14/26 16:38:04.607
  STEP: verifying migration output files exist @ 05/14/26 16:38:06.741
  STEP: applying generated Gateway manifests (dry-run mode) @ 05/14/26 16:38:06.742
  STEP: verifying generated resource counts @ 05/14/26 16:38:08.302
  STEP: verifying Gateway has dry-run annotation @ 05/14/26 16:38:08.466
  STEP: waiting for Gateway dry-run-plan annotation @ 05/14/26 16:38:08.466
  STEP: verifying NO ALB is created for dry-run Gateway @ 05/14/26 16:38:08.484
  STEP: removing dry-run annotation to trigger real reconciliation @ 05/14/26 16:39:08.485
  STEP: waiting for Gateway ALB to be provisioned @ 05/14/26 16:39:08.528
  {"level":"info","ts":1778801952.7843359,"msg":"waiting for gateway ALB to be available"}
  STEP: comparing ALB configurations: listeners, rules, and target groups @ 05/14/26 16:41:59.41
  STEP: comparing ALB configurations: tags @ 05/14/26 16:41:59.663
  STEP: verifying traffic to Gateway ALB @ 05/14/26 16:42:00.281
  {"level":"info","ts":1778802120.281466,"msg":"waiting for LB DNS to be resolvable","dns":"k8s-i2ge2eaf-e2emiggr-f36dbdb3cd-1457840818.us-west-2.elb.amazonaws.com"}
  STEP: teardown sandbox namespace @ 05/14/26 16:42:00.394
• [513.037 seconds]
------------------------------

Ran 2 of 2 Specs in 521.202 seconds
SUCCESS! -- 2 Passed | 0 Failed | 0 Pending | 0 Skipped
PASS

• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

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This pull-request has been approved by: shuqz

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.23%. Comparing base (22cdb42) to head (49fcd0d).
⚠️ Report is 21 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4739      +/-   ##
==========================================
+ Coverage   56.09%   56.23%   +0.13%     
==========================================
  Files         388      389       +1     
  Lines       30932    31043     +111     
==========================================
+ Hits        17352    17456     +104     
- Misses      12566    12575       +9     
+ Partials     1014     1012       -2     

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