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

Commencez par examiner le travail existant sur la branche dev du fork de l’auteur ainsi que les issues et PRs liées #1901 et #1903. Clarifiez le comportement attendu du projet pour l’AST et les dialectes concernant CREATE PROCEDURE, puis ajoutez des tests couvrant la prise en charge convenue afin que le SQL valide soit analysé comme prévu.

Rédigé par le modèle d'indexation à partir du texte de l'issue.