Move test_requires to build_requirements in tests

[czoido]

Changelog: Fix: Move test_requires to build_requirements method in tests.
Docs: Omit

[memsharded]

This change is good from the documentation and good-practices point of view.
But it sounds that the test suite should still keep some case that checks that a test_requires() keeps working inside a requirements() method, as this has been traditionally allowed, and if Conan started raising errors if this changed, in a breaking behavior, we wouldn't notice because the test suite no longer covers that case.

[czoido]

This change is good from the documentation and good-practices point of view. But it sounds that the test suite should still keep some case that checks that a test_requires() keeps working inside a requirements() method, as this has been traditionally allowed, and if Conan started raising errors if this changed, in a breaking behavior, we wouldn't notice because the test suite no longer covers that case.

I was thinking about leaving one in requirements or a new test that tests that explicitly?

[memsharded]

I was thinking about leaving one in requirements or a new test that tests that explicitly?

Probably leaving one in requirements, adding a explicit comment about the intent to test that, but that is not recommended