Inline the content to avoid a round-trip through qjsonarray.cpp and
qjsonobject.cpp.
This change revealed an inadviseable unit test check that dereferences
the end() iterator to get its type. I haven't changed it, but have
marked with ###. I also fixed a likely copy&paste mistake in that test.
Change-Id: I89446ea06b5742efb194fffd16bb774f3bfbe5f5
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>