1) Update global_config.py  and add RHEL8.8 and RHEL9.2 OS versions.

2) Drop RHEL8.6 and RHEL9.0 OS versions.

3) RHEL 8.8 GA is May 16th 2023 and RHEL9.2 GA is May 9th 2023

4) We need to update the RHEL 8.8 and RHEL9.2 images at http://cnv-qe-server.rhos-psi.cnv-qe.rhood.us/files/cnv-tests/rhel-images/

Important Note: We need to do this for 4.13.0.