[backport -> release/3.6.x] fix(vault): use global query when finding a vault by prefix

[team-gateway-bot]

Automated backport to release/3.6.x, triggered by a label in #12572.

Original description

Summary

In FTI-5762 it was reported that there is a problem with secret rotation when vaults are stored inside a workspace. This commit will fix it by passing workspace = null aka making a call a global call which will not then use the possibly incorrect workspace (default) to find vault entity (the vault config). The vault entity prefix is unique across workspaces.

Checklist

• [ ] 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
• [ ] There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

Fix FTI-5762