tentacle: tentacle-p2p add centos9 to stress-split

tentacle: tentacle-p2p add centos9 to stress-split

Adds CentOS 9 Stream as a supported host OS for the tentacle-p2p
stress-split suite.

Rocky10 is not added here. This suite tests a bare-metal p2p upgrade
between Tentacle point releases. Rocky10 package support was added during
that release cycle, meaning there is no valid "FROM" package baseline to
install on Rocky10, making a bare-metal point-to-point upgrade path on Rocky10
impossible to test.

Fixes: https://tracker.ceph.com/issues/76710
Signed-off-by: Nitzan Mordechai <nmordech@ibm.com>