Create Connection::executeIfTableExists

Problem/Motivation

PostgreSQL does not like it when you query a table that does not exist in the database. Now are we fixing that by wrapping every query on PostgreSQL in a transactional save point. That results in a lot more round trips to the database for PostgreSQL. The meta issue for this is #3615690: Removal of unnecessary savepoints from PostgreSQL. In this issue we are adding the method Connection::executeIfTableExists(), which should be called before running the query on a table that might not exist. This issue is the followup of #2371709: Move the on-demand-table creation into the database API.

Proposed resolution

Add the method Connection::executeIfTableExists()

Remaining tasks

TBD

User interface changes

None

Introduced terminology

None

API changes

The method Connection::executeIfTableExists() has been added.

Data model changes

None

Release notes snippet

TBD