fix: Enable PostgreSQL stream selection for c9s and RHEL9

c9s/RHEL9 provides PostgreSQL 13 as default system version as classic
RPM package, butalteranative versions are provided as a modular content.
So it requires different instalation procedure.

Author: fila43

vars/CentOS_9.yml

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: MIT
+---
+# Put internal variables here with CentOS 9 specific values.
+
+tasks:
+  - name: Set PostgreSQL packages based on version
+    set_fact:
+      __postgresql_packages: >-
+        {{ ['@postgresql:' + postgresql_version +
+             '/server'] if postgresql_version != '13' else
+             ['postgresql-server'] }}

vars/RedHat_9.yml

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: MIT
+---
+# Put internal variables here with Red Hat Enterprise Linux 9 specific values.
+
+tasks:
+  - name: Set PostgreSQL packages based on version
+    set_fact:
+      __postgresql_packages: >-
+        {{ ['@postgresql:' + postgresql_version +
+             '/server'] if postgresql_version != '13' else
+             ['postgresql-server'] }}