fix(admin_api): allow retrieval via uuid names

[nowNick]

Summary

Previously you could name an entity using a uuid however it wouldn't be retrievable from the API by it's name.

Example: GET /routes/<uuid> - where uuid was set as this route's name.

This PR fixes that.

This PR changes behaviour of PUT operation as upsert with uuid-name as described in the docs PR: https://github.com/Kong/docs.konghq.com/pull/7107

Checklist

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

Issue reference

KAG-2581