* Work correctly if an additional fresh module imports other
additional fresh module which imports a blocked module.
* Raises ImportError if the specified module cannot be imported
while all additional fresh modules are successfully imported.
* Support blocking packages.
* Always restore the import state of fresh and blocked modules
and their submodules.
* Fix test_decimal and test_xml_etree which depended on an undesired
side effect of import_fresh_module().
(cherry picked from commit ec4d917a6a)
