Smart file grouping not consistent

[markcmiller86]

Describe the bug

I copied a file ugrid_mixed_cells.vtk four times creating ugrid_mixed_cells01.vtk ... ugrid_mixed_cells04.vtk.

I did the same thing with a different extension, .h5m.

VisIt's smart file grouping recognizes the first set as a group but not the second.

I believe the logic is somewhere near here...

https://github.com/visit-dav/visit/blob/d1fbae6caeb3364954f3c2b54eb0a27ae69fd889/src/mdserver/main/MDServerConnection.C#L1807

and I am thoroughly stunned how complex that block of code is.