The previous approach relied on finding an arbitrary QTabBar then
looking for siblings of that QTabBar. However there were several
drawbacks of that approach

1) The arbitrary QTabBar may not be discoverable using the unnamed
object naming scheme.  This was the case in at least one instance where
the object was named 1QTabBar16 when recorded on Linux, but when played
back on Windows there weren't 16 hidden QTabBar children of QMainWindow.

2) The previous approach was documented to be specifically for
QDockWidgets, but was not guarded as such.  i.e. Anytime the named tab
is not found it will revert to looking for siblings even for named
objects or unnamed QTabBars that aren't children of QMainWindow.

This commit also fixes incorrect qCritical() usage.  Since qCritical()
causes program termination, there must be only one call with the full
message, rather than multiple calls with partial messages.  I suspect
Paraview installs a qtMessageHandler that doesn't cause program
termination since there is also an error flag.