BUG #14338. Fix build issues with vtkhdf5.

vtkhdf5 is not a linkable target when using external HDF5. One must use the
module API to ensure that the linking works correctly in cases where HDF5 is
external or internal.

Change-Id: I60223a0c69a4f4748c0f7db392a11be58ec2a1f4
BUG #14263: Fix pvpython in installed ParaView.

Fixes the issue commit 8bd0620b attempted to fix. We need to add the location of
*Python.so files to sys.path since they are no longer in the same place as the
ParaView shared libraries. Fixed that by correcting the typo in commit
8bd0620b.

Change-Id: Ic5b7618e09a5423d9ae8d89bf0f51e80861883d0
Merge topic '14263_fix_python_in_installs' into next

3413451 BUG #14263: Fix pvpython in installed ParaView.
Merge topic '14338_fix_build_issues' into next

ba2fda5 BUG #14338. Fix build issues with vtkhdf5.