Revert "Sort alltests test section alphabetically."

This reverts commit 9a6579a1bf7a06c4adad38d8ead94d0e6e9fcfb5.
Revert "Remove dexterit test group."

This reverts commit 9e32f53c64ff837d01b4b5369d8308ebd56804f4.
Revert "Remove plone_app_testing alltests test group. We should try to get rid of as many test groups as possible in order to identify the packages that have test isolation problems. So we can get rid of them in the long term."

This reverts commit 641807eeb1ef81e17f861744db1dacb2562bef12.