Update migration guide and documentation

Description

https://hibernate.atlassian.net/browse/HHH-11023 introduced a change that
may require the user to specify the default_schema and/or default_catalog for the schema generation/migration tools to work.

Environment

None

Status

Assignee

Gail Badner

Reporter

Andrea Boriero

Fix versions

Labels

None

backPortable

None

Suitable for new contributors

None

Requires Release Note

None

Pull Request

None

backportDecision

None

Affects versions

5.2.10
5.1.7

Priority

Major