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.

Esamina prima la PR #2138 per comprendere i metadati delle relazioni autoreferenziali e il flusso della mutation di creazione multipla. Traccia la generazione delle query e i percorsi di mutation rimanenti, quindi verifica che gli elementi di primo livello e quelli correlati vengano creati nell’ordine corretto per le relazioni autoreferenziali.

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