Because @coversDefaultClass doesn't indicate any coverage (it's
just an alias to avoid having to write the class name in @covers),
this commit fixes all the files that were using that annotation
and missing any @covers.
Basically, replacing one by the other and done.
These are the only cases 100% safe to apply the renaming of the
testcase class names to match the file names.
All other cases are not safe, because they are missing namespace
and may enter into name conflicts. Adding namespaces is not as
simple as imagined because it implies to, also, add a good number
of modifications to core. See the issue for more details.
