Migrate from cnpg-ibm to ibm-pg-operator

[Daniel-Fan]

What this PR does / why we need it:

This PR updates the PostgreSQL operator integration by migrating from the cnpg-ibm operator to the new ibm-pg-operator. The changes include:

1. Updates the API group from postgresql.cnpg.ibm.com to pg.ibm.com across all resource definitions
2. Updates the operator package name from cnpg-ibm to ibm-pg-operator
3. Updates the operator channel from stable-v1.25 to stable-v1.28
4. Updates the ConfigMap reference from cnpg-ibm-operand-images-config to ibm-pg-operator-operand-images-config
5. Removes the separate ibm-cnpg-postgres-operator operator installation and consolidates to a single common-service-cnpg operator
6. Removes the cnpg-postgresql-operator-request OperandRequest resource as it's no longer needed
7. Updates catalog source references to use the common catalog source variable
8. Updates RBAC permissions to reflect the new API group

Which issue(s) this PR fixes:
Fixes https://github.ibm.com/IBMPrivateCloud/roadmap/issues/69032

[YCShen1010]

/lgtm

[YCShen1010]

thank you @Daniel-Fan for the great job