Prior to this commit it was possible to set or get a static field using
ReflectionTestUtils but only if an instance of the target class was
available.
This commit introduces dedicated support for setting and getting static
fields in ReflectionTestUtils when only the target class is available.
Furthermore, this commit increases the robustness of
ReflectionTestUtilsTests regarding expected exceptions and simplifies
the Javadoc for ReflectionTestUtils.
Issue: SPR-6792
063ef240c1