[Feature] Use snaphost to start replica in the same region

[xgerman]

Assuming disk snashots are only available in the same regions use a snapshot when a replcia is added (via add region) in the same region. See https://techcommunity.microsoft.com/blog/adforpostgresql/supporting-chatgpt-on-postgresql-in-azure/4490247 for more information on this optimization.

We will need to do some research on how other stoatge providers/clouds handle this and potentially change CNPGs add replica mechanism (do soemthing isntead of pgbasebackup).