Add find_package in support files?

[sloriot]

Consistency is a great thing so having all packages handled similar is the best, though I think that all packages should have the find inside so that maintenance will be easier as well.

Originally posted by @albert-github in https://github.com/CGAL/cgal/pull/9112#discussion_r2469525955

[LOTUS9679]

Hi @sloriot, I am interested in working on this CMake consistency issue.

Could you point me to an example of a "support file" that currently handles the find_package correctly, and one that needs to be updated? I want to make sure I follow the intended pattern.