Honor --graphql.nested-create.enabled option for other database types

Related Issue : [#1950](https://github.com/Azure/data-api-builder/issues/1950)

At the moment, nested create operation is applicable only for MsSQL database type. So, the option `--graphql.nested-create.enabled` option is honored only for MsSQL. When nested create operation is supported for other database types, the option `--graphql.nested-create.enabled` has to be honored as well.

This issue tracks the effort needed for honoring the CLI option.

Start by reading related issue #1950 to understand when nested create is expected for the other database types. Then trace handling of the `--graphql.nested-create.enabled` CLI option across the nested-create implementation and database-specific paths. Done means the option is honored consistently wherever nested create is supported, with coverage for each supported database type.

Scritto dal modello di indicizzazione a partire dal testo della issue.