BUG: 14544: Fix xdmf file series.

Added support for xmf file series for Xdmf reader. Currently the reader only
supported a single xmf file containing temporal collection. Fixes issue seen in
BUG #14544.

Change-Id: Ie358af8460fb036d4807c46e3cf832bf2f91bba2
Merge topic '14544_temporal_xdmf' into next

726de05f BUG: 14544: Fix xdmf file series.