[Image Update] postgresql to version 15

#### Which image would you like to change?

base

#### What changes are you requesting?

Update of postgresql, postgresql-devel, postgresql-libs to version 15

#### What scenario are these changes enabling?

Currently pg tools cannot be used against the latest postgres version 15

```
pg_dump -Fp -v -h fqdn --port=5432 --username=postgres --dbname=test -f test.dump
pg_dump: error: server version: 15.2; pg_dump version: 14.8
pg_dump: error: aborting because of server version mismatch
```

#### By how much does this change change the image size?

Not sure, the size difference depends on the rpm packaging differences between version 14 and 15 of postgres.

#### Extra information

The cloud shell needs to track the releases of databases, for example at https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/release-notes#release-july-2023 or https://learn.microsoft.com/en-us/azure/mysql/concepts-version-policy, so it always matches the latest Azure GA database version. Are are able to setup a process to make this happen?