OpenCDC integration + other fixes

[lovromazgon]

Description

Updates SDK to the latest version and integrates OpenCDC record into the connector. I also took the opportunity to fix some inconsistencies, for example:

• destination test now uses global test utilities to prepare the database
• key column is included in payload in logrepl.SnapshotIterator to match CDC behavior and longpoll.SnapshotIterator
• position in longpoll.SnapshotIterator was changed to match position in logrepl.SnapshotIterator
• decoding of values was simplified and uses info from the library instead of our pgutil package which was now removed
• introduced constants for metadata and config fields - metadata field for table now has the prefix postgres.* to prevent conflicts with metadata from other connectors
• global statement builders were replaced with local ones for each struct that needs it

Code should be a bit simpler now, this can already be seen from the line number diff.

Depends on ConduitIO/conduit-connector-sdk#31 (needs to be merged and we need to update the connector SDK version).

Related to ConduitIO/conduit#512.

Quick checks:

• I have followed the Code Guidelines.
• There is no other pull request for the same update/change.
• I have written unit tests.
• I have made sure that the PR is of reasonable size and can be easily reviewed.

[hariso]

🚀

[hariso]

👍