tst_qmllint: Organize test files

Test files should be grouped into subfolders instead of using prefixes.
i.e. all unqualified access tests should get their own directory etc.

As a general rule if there are more than two tests, they should get their own subdirectory. Do keep in mind that some of them might depend on other types and if they are not used anywhere else they should also be moved into the subdirectory (You will see whether that's the case by seeing if any tests fail if you move a file).