[Snapshots] Option to use PK instead of ctid ranges

[eminano]

Is your feature request related to a problem? Please describe.
Have the option to provide a PK column for a table to be used during the snapshot process instead of using the ctid, which forces a range over a stable view of the database (transaction snapshot). This is helpful for enabling resumable snapshots at row level as well as reconnection attempts.

Describe the solution you'd like
Have a data snapshot generator implementation that uses PK to read the source table instead of relying on transaction snapshots and ctid ranges.