[DEV-15225] Fix postgres db name and recreation (#555)

[ltellesfl]

Note

Medium Risk
Changes Crunchy Postgres instance-set naming/label selectors and pod anti-affinity rules, which can affect Postgres pod scheduling and may trigger instance/pvc recreation if names no longer match existing clusters.

Overview
Adjusts Crunchy Postgres instance scheduling so pod anti-affinity targets the postgres-data cluster (instead of postgres-insights) for the on-prem instance specs.

Makes the non-on-prem Crunchy instance-set name configurable via new crunchy_instance_name (default pgha1) and uses it consistently in the instance name and the anti-affinity postgres-operator.crunchydata.com/instance-set selector.

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