Bug#1000611: libvtk9{,-qt}: soname change without library transition

[Adrian Bunk]

Package: libvtk9
Version: 9.1.0+dfsg2-2
Severity: serious
Control: affects -1 libvtk9-qt src:vtk9

https://ci.debian.net/data/autopkgtest/testing/amd64/f/freecad/16980590/log.gz

...
ERROR: TestFemApp (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: TestFemApp
Traceback (most recent call last):
  File "/usr/lib/python3.9/unittest/loader.py", line 154, in loadTestsFromName
    module = __import__(module_name)
  File "/usr/share/freecad/Mod/Fem/TestFemApp.py", line 33, in <module>
    from femtest.app.test_mesh import TestMeshCommon as FemTest07
  File "/usr/share/freecad/Mod/Fem/femtest/app/test_mesh.py", line 33, in <module>
    import Fem
ImportError: libvtkFiltersExtraction-9.0.so.1: cannot open shared object file: No such file or directory
...


The soname of the vtk9 libraries is not 9, it is 9.0 for VTK 9.0
and 9.1 for VTK 9.1:

$  objdump -p /usr/lib/x86_64-linux-gnu/libvtkChartsCore-9.1.so.1 | grep SONAME
  SONAME               libvtkChartsCore-9.1.so.1
$

In bullseye libvtk9 and libvtk9-qt should have been named
libvtk9.0 and libvtk9.0-qt, but this alone is harmless.

Not harmless is that the libraries must transition to the new
soname in 9.1, renaming the packages to libvtk9.1 and libvtk9.1-qt.