fix(request-debugging): add missing `router` section of the timing output

[ADD-SP]

Blocked by https://github.com/Kong/kong/pull/12580

Summary

We have already added calls of the hook to measure the time consumed by the router.

https://github.com/Kong/kong/blob/f7e6eeefe006af11129d1b0e39a1c06449a53d42/kong/runloop/handler.lua#L1152-L1162

But forgot to setup the hook function, this PR setups the hook function for the router.

And also fix some tests that might cause flakiness.

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

Issue reference

KAG-3438