sea-orm-cli: Add support for postgres inheritance

[alfalcon90]

Motivation

sea-orm-cli generate entity does not currently generate entities from tables using inheritance.

Proposed Solutions

For entity generation every table that uses the INHERITS statement should be generated as an entity and the base table should be ignored

[alfalcon90]

Relevant discussion: https://github.com/SeaQL/sea-orm/discussions/2412