Report runtime linker search path to VTK clients

Add a <module>_RUNTIME_LIBRARY_DIRS module information value.  Teach
vtk_module_config to report <ns>_RUNTIME_LIBRARY_DIRS by collecting and
de-duplicating the directories from the modules.

This restores the VTK_RUNTIME_LIBRARY_DIRS value provided by VTKConfig
prior to modularization.  It is useful for consuming applications to
find their runtime library files for packaging.

Change-Id: I488d5c1395203a2492a4f5cc9b3c1d97385a31c3
Merge topic 'module-RUNTIME_LIBRARY_DIRS' into master

dd4b51b9 Report runtime linker search path to VTK clients