Support non default schemas when migrating from SqlP

[andreasohlund]

Requested by user Particular/docs.particular.net#5590

[DavidBoike]

This also may affect migration to SQL Transport native timeouts, so a comprehensive review of schema usage (or non-usage) in all SQL-related sources & targets should be performed.

See this line in SqlTEndpointTarget.cs where a schema is not added to the migration table. It should also be evaluated whether a staging table needs to support a custom schema. Either way, the result should be documented.