refactor(shorthand_fields): remove translate_backwards in favor of replaced_with

[nowNick]

Summary

We've introduced replaced_with when working on shorthand_fields when used as deprecation and making sure that incoming request do not contain mismatched data: #13565

This made translate_backwards field obsolete as replaced_with is just more robust and intuitive. This PR removes that code.

Checklist

• N/A The Pull Request has tests
• N/A A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• N/A There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

KAG-5298

[bungle]

Just trying to make this more readable, I think you get an idea from this and can work forward on it.

[team-gateway-bot]

Cherry-pick failed for master, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git remote add upstream https://github.com/kong/kong-ee
git fetch upstream master
git worktree add -d .worktree/cherry-pick-13604-to-master-to-upstream upstream/master
cd .worktree/cherry-pick-13604-to-master-to-upstream
git checkout -b cherry-pick-13604-to-master-to-upstream
ancref=$(git merge-base a6ccbb1af2169a9edbf4491a91ecaf5d2d7fb067 fe67a1ef4d903b4fddbbd72a93a7faa5853cdd73)
git cherry-pick -x $ancref..fe67a1ef4d903b4fddbbd72a93a7faa5853cdd73