Support multiple create mutation for self-referencing relationships.

PR https://github.com/Azure/data-api-builder/pull/2138 adds support for querying relationships that reference the same entity (self-join tables).

Extend multiple create functionality to support relationships that reference itself.

Some things to consider are:
- Accurate determination of referencing/referenced entity. Though, referenced and referencing entity are both the same, we need to be able to identify whether **top level item** (or) **related item** should be created first.
- The current data structure maintains the relationship metadata at the entity level. PR https://github.com/Azure/data-api-builder/pull/2138 introduces changes to maintain the relationship metadata at the granularity level of relationship. This new data structure should be used during query generation and rest of the mutation flows.

Revisa primero el PR #2138 para entender los metadatos de las relaciones autorreferenciales y el flujo de la mutación de creación múltiple. Traza la generación de consultas y las rutas de mutación restantes, y luego verifica que los elementos de nivel superior y los relacionados se creen en el orden correcto para las relaciones autorreferenciales.

Escrito por el modelo de indexación a partir del texto del issue.