Update more tests. Second round

This MR brings several refactoring changes to handle unit tests. The most relevant change is that the different xxx_files_list (finders) are split into two:

1. The actual regular expressions, globs, etc, per each category. An array of strings similar to what the recipe defines
2. The validated files found once the recipe is built and installed. A dict with a relation of a file entry on 1 as key and the actual files found as the value.

The situation I was facing during the test migration was that the "finders" were not consistent about their returned values:

1. Some were returning a list of potential files (not validated)
2. Some others were returning a file list of only the existing files on the prefix
3. Some others were returning a more complex algorithm, implying local build tools, like on the DLL or .pdb cases.

So all of them finders are now split and consistent on the expectations of the caller with the function parameter "only_existing" being by default True to be consistent with the current way of working.

Not validating a file in the prefix is not an error for now. I just wanted to validate the idea. You can see on the CI some warnings about files not found on the prefix, which is something good; before, it was silently passing because the list of files was never returning some of them (because they were not found), and therefore, for the packager, it was fine.

The rest are just specific fixes for some test's corner cases. In any case, the names chosen are not the best names and can be easily modified.