Migrate Postgres DB for airflow

• Airflow is currently using postgresql single server with postgres version 10.
• Azure Database for PostgreSQL Single Server will be retired in March 2025.
• Migration to flexible server is necessary to use PostgreSQL versions > 10
• Refer Azure postgresql migration tool
• Pertaining to above reasons upgrading airflow db to flexible server with postgresql 14 version is recommended.

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• Currently, Apache airflow uses Pgbouncer to do connection pooling.
• It is using outdated mcr.microsoft.com/azure-oss-db-tools/pgbouncer-sidecar:pgbouncerv1.13
• Since Postgresql flexible server natively supports pgbouncer, https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/concepts-pgbouncer It is advisable to use it.
• It would require helm changes to disable pgbouncer in helm charts and modify port configs and few other connection config changes.

Related to #324 (closed)