Deprecating VxFlexOS for rebranding

VxFlexOS is rebranded to Powerflex.
cinder::backend::dellemc_vxflexos is deprecated,
use rebranded resource cinder::backend::dellemc_powerflex instead.

Depends-On: https://review.opendev.org/#/c/742016/
Change-Id: Ib88500a765c29a887c58c21d31cd39fcc43c7f6c

manifests/backend/dellemc_vxflexos.pp

@@ -120,6 +120,9 @@ define cinder::backend::dellemc_vxflexos(
 
   include cinder::deps
 
+  warning('The cinder::backend::dellemc_vxflexos is rebranded and deprecated. It will be removed \
+    in W-release, please use cinder::backend::dellemc_powerflex resource instead.')
+
   cinder_config {
     "${name}/volume_driver":                           value => 'cinder.volume.drivers.dell_emc.vxflexos.driver.VxFlexOSDriver';
     "${name}/san_login":                               value => $san_login;

releasenotes/notes/vxflexos-driver-deprecate-f428e372280c44e4.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - VxFlexOS is rebranded to Powerflex.
+    cinder::backend::dellemc_vxflexos is deprecated and will be removed in
+    W-Release. Use rebranded resource cinder::backend::dellemc_powerflex.