Python: deprecate 3.8 (#46913)

* Python: deprecate 3.8

* Remove preference for EOL Python versions

* Explicitly deprecate things requiring EOL Python

* More deprecations

* deprecate old versions of slepc, py-petsc4py, py-slepc4py in sync with old versions of petsc

---------

Co-authored-by: Satish Balay <balay@mcs.anl.gov>

share/spack/gitlab/cloud_pipelines/stacks/e4s-cray-rhel/spack.yaml

@@ -51,8 +51,6 @@ spack:
     paraview:
       # Don't build GUI support or GLX rendering for HPC/container deployments
       require: "@5.11 ~qt ^[virtuals=gl] osmesa"
-    python:
-      version: [3.8.13]
     trilinos:
       require:
       - one_of: [+amesos +amesos2 +anasazi +aztec +boost +epetra +epetraext +ifpack
@@ -106,7 +104,7 @@ spack:
   - lammps
   - legion
   - libnrm
-  #- libpressio +bitgrooming +bzip2 ~cuda ~cusz +fpzip +hdf5 +libdistributed +lua +openmp +python +sz +sz3 +unix +zfp +json +remote +netcdf +mgard # mgard: 
+  #- libpressio +bitgrooming +bzip2 ~cuda ~cusz +fpzip +hdf5 +libdistributed +lua +openmp +python +sz +sz3 +unix +zfp +json +remote +netcdf +mgard # mgard:
   - libquo
   - libunwind
   - mercury

share/spack/gitlab/cloud_pipelines/stacks/e4s-cray-sles/spack.yaml

@@ -44,8 +44,6 @@ spack:
     paraview:
       # Don't build GUI support or GLX rendering for HPC/container deployments
       require: "@5.11 ~qt ^[virtuals=gl] osmesa"
-    python:
-      version: [3.8.13]
     trilinos:
       require:
       - one_of: [+amesos +amesos2 +anasazi +aztec +boost +epetra +epetraext +ifpack