Enhancement: Remove the SchemaSeparator property from the IDbSetting interface

[mikependon]

As part of the extensibility capability of RepoDb, we had introduced the SchemaSeparator property in the IDbSetting interface.

With the knowledge we have after asking the community, and also based on our internal assessment, all the current supported RDBMS (and the future RDBMS to be supported) will most likely be using the . schema separator.

Action Items:

• Remove the usage of this property in the RepoDb Core code base.
• Pre-assume in all code-lines to write the . character when separating the Schema and Table.
• Add the Obsolete attribute so the consumers will not be affected.
• All the extension libraries must follow the changes.

Acceptance Criteria

• All the existing Unit and Integration Tests must "still" be running and all green (within the Core and the Extended libraries).
• Remove the unnecessary Unit Tests and Integration Tests.

[mikependon]

This is now a part of the latest deployment at RepoDb (v1.11.6).