RTA: verify that 5.15.x LTS commercial and 5.15.x LGPL source package content are equal

The only difference between the 5.15 LTS commercial and LGPL source packages should be that the commercial license headers are used in the commercial source package. So, e.g.

• the amount of files & folders and the name of files & folders should be equal in the source packages.
• If possible, it would be good to verify the size of the source packages too.
• please verify also the content of the submodules source packages (instead of testing just the single source package)

Qt 5.15.3 commercial sources in the archive:

http://ci-files02-hki.intra.qt.io/packages/jenkins/archive/qt/5.15/5.15.3-final-released/latest/src/

Qt 5.15.3 LGPL sources in the archive:

http://ci-files02-hki.intra.qt.io/packages/jenkins/archive/qt/5.15/5.15.3-lgpl-src-package/src/

--> later 5.15.x LTS releases will have same kind of paths in the archive.

Note! this test case needs to be run only for the 5.15.x opensource releases.