BUG: Name SampleData internal widget for easy referencing by QtTesting

See #2808

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22261 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Always build qSlicerPersistentCookieJar

It is being used by qSlicerWebWidget which is not conditionally built by
Slicer_BUILD_EXTENSIONMANAGER_SUPPORT

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22262 3bd1e089-480b-0410-8dfb-8563597acbee