Revert 754b8d4dbd0ecfb21ffcec4793a4aeab2de57de4

This reverts "Moved closure_0XX.phpt into their own folder; I need to rerun
them often for a bug I am working" because Stas doesn't like it.

This reverts commit 754b8d4dbd0ecfb21ffcec4793a4aeab2de57de4.
Added smaller tests related to bug 66622.