Merge tags from alb.ingress.kubernetes.io/tags

[oliviassss]

Issue

Fixes #2411

Description

This PR will merge the tags specified by alb.ingress.kubernetes.io/tags from ingress and service and add them to the corresponding target groups. In case of conflicting values for the tag key, controller gives precedence to the ones specified on the service.

Test

• Added unit test
• Created ingress and backend service, verified that the target group has merged tags specified from both ingress and service, and the tags of ingress will not be affected
• Created ingress and beckend service with conflicted tag keys, verified that the target group has the tag values from service for the conflicted tag keys
• Created IngressClass, ingress and backend service, verified that the tags specified via IngressClass still have higher priority than tags specified via annotation on ingress or service

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
• 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 🌟

[k8s-ci-robot]

Hi @oliviassss. Thanks for your PR.

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[kishorj]

/ok-to-test

[kishorj]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kishorj, oliviassss

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[kishorj]

/retest