Improving support for `CREATE PROCEDURE`

sqlparser-rs currently doesn't have great support for `CREATE PROCEDURE` statements, leading to parser errors when I pass in valid SQL. I'd like to work on improving this (I've already started on [my fork](https://github.com/ZacJW/sqlparser-rs/tree/dev)).

What's the project's ideal vision for how this would be handled? Stored procedures are the kind of thing that can be very RDBMS specific. Do you just want the AST to cover what's in the standard, but the dialects to accept but discard additional options?

The first fix which will be ready to go once I've written tests is #1901, support for what PostgreSQL calls argmode and the standard calls parameter mode.

## PRs

- #1901
- #1903

Inizia esaminando il lavoro esistente sul branch dev del fork dell'autore e le issue e PR collegate #1901 e #1903. Chiarisci il comportamento previsto del progetto per AST e dialetti relativamente a CREATE PROCEDURE, quindi aggiungi test che coprano il supporto concordato, in modo che l'SQL valido venga analizzato come previsto.

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