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

Comece revisando o trabalho existente no branch dev do fork do autor e as issues e PRs vinculadas #1901 e #1903. Esclareça o comportamento pretendido do projeto para AST e dialetos com CREATE PROCEDURE e, em seguida, adicione testes que cubram o suporte acordado, para que SQL válido seja analisado conforme esperado.

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