tentacle: suites/upgrade add centos to centos image upgrade

tentacle: suites/upgrade add centos to centos image upgrade

Previously, each suite had a single upgrade-sequence.yaml that targeted
only one image.
This commit splits each upgrade sequence into two variants teuthology
picks one per run

  upgrade-sequence$/centos-stream9.yaml  - targets $sha1
  upgrade-sequence$/rockylinux-10.yaml   - targets $sha1-rockylinux-10

This applies to:
 - reef-x/parallel
 - reef-x/stress-split
 - squid-x/parallel
 - squid-x/stress-split
 - telemetry/reef-x
 - telemetry/squid-x

For the stress-split suites, the upgrade logic is split into a
first-half-sequence run concurrently with thrashosds,
and a second-half-sequence run after.
Both sequences contain the hardcoded target image, so each variant
needs its own copy. They were previously inlined in 1-start.yaml.

This commit extracts them into the upgrade-sequence$/ files so
each variant can target the right image.

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