tests(*): fix an error in http_mock template

[outsinre]

Summary

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

Fix #FTI-5807
Fix #KAG-4087

[StarlightIbuki]

Oops!
We need also to check if we use the name in tests and fix them.
Also, my original intention was to name them following the phase handlers so header_filter and body_filter should be the right name.

[outsinre]

Another inconsistency:

https://github.com/Kong/kong/blob/master/spec/helpers/http_mock.lua#L85C41-L89 and https://github.com/Kong/kong/blob/master/spec/helpers/http_mock/template.lua#L143.

[StarlightIbuki]

Another inconsistency:

master/spec/helpers/http_mock.lua#L85C41-L89 and master/spec/helpers/http_mock/template.lua#L143.

That's an outdated comment issue. Please fix them together.

[hanshuebner]

Please fix the PR title and description. What is the problem? How is it fixed?

[outsinre]

As this is not an urgent task, will come back after 3.7.0 PR.