Allow running unit tests located outside /tests folder

[DavidSannier]

Description

While running make test:all the output shows
[...]
Testing basic
[...]
Testing debounce_sym_defer_pk
[...]
But running make test:debounce_sym_defer_pk does not run the specified tests as it does for make test:basic

Fix test filter comparison for tests included by builddefs/testlist.mk

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).