fix(ai-proxy): (multiple)(AG-154) fixed tools-functions calls coming back empty

[tysoekong]

Summary

• Fixes Bedrock, Gemini, Anthropic, Cohere function calling in AI-Proxy system (AG-154)
• Fixes "image_url" type message not working in Bedrock (AG-155)

Checklist

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

Issue reference

AG-154
AG-155
AG-166

[tysoekong]

@fffonion @subnetmarco Let's go

[tysoekong]

spec/03-plugins/39-ai-request-transformer/02-integration_spec.lua is a genuine failure. I never get this right first-go, argh.

I'll fix it...

[oowl]

Also, we need some test for the current fix.

[tysoekong]

@oowl I am on it

[tysoekong]

@oowl Added tests

[fffonion]

cherry-pick in https://github.com/Kong/kong-ee/pull/10757

[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-13760-to-master-to-upstream upstream/master
cd .worktree/cherry-pick-13760-to-master-to-upstream
git checkout -b cherry-pick-13760-to-master-to-upstream
ancref=$(git merge-base c5199ff0c386bc8091273c8a99d6760eb382f102 e659e37b9832fd57aa970545244dec76d4b23210)
git cherry-pick -x $ancref..e659e37b9832fd57aa970545244dec76d4b23210

[team-gateway-bot]

Backport failed for release/3.8.x, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin release/3.8.x
git worktree add -d .worktree/backport-13760-to-release/3.8.x origin/release/3.8.x
cd .worktree/backport-13760-to-release/3.8.x
git switch --create backport-13760-to-release/3.8.x
git cherry-pick -x e5f5ca82a96fd860283580d2c1680580909c842e 042848703e56fef53b58b9fa49bf4c38b0b4035f 720ab027a02078ddafe04eb2cdceba799405c81f d19edcfea9fdfaf7733fe4cfeb3df81a8d5b9f27 db9d6ae7a9987e3a29efd20ad66122d3b834813e