Add custom operation generation

[DamianCzajkowski]

Pull Request Description

Note:
This pull request will be merged into another branch and deployed as a dev version (experimental). I want to test in some real projects. The code needs a refactor and some optimization.

This pull request introduces custom operation generation in ariadne-codegen. The following features have been implemented and tested:

• Query generation
• Mutation Fields
• Mutation generation
• Response types (moved to a separate issue)
• Scalars/Unions as a response
• Turn off queries need validation when custom generation is on
• Add selection on which queries/mutations custom operations can be done (to generate fewer classes) (moved to a separate issue)
• Add more tests
• Add examples of usage (new tests are the perfect example)

Response Types Generation

I attempted to generate response types using Pydantic classes. However, Pydantic version 2 is significantly slower. In the context of Saleor, which involves linking 81 classes, importing a single class from such a file takes approximately 7 seconds. Due to this performance issue, I am considering switching to regular dataclasses with custom functions for data type validation. This approach aims to improve performance while maintaining flexibility and robustness in type validation.

Feel free to review the changes and provide feedback!

Simple example:

    async with SaleorClient(saleor_url=saleor_url, api_key=None) as saleor_client:
        query_str = [
            Query.products(first=1, channel="default-channel").fields(
                ProductCountableConnectionFields.edges().fields(
                    ProductCountableEdgeFields.node().fields(
                        ProductFields.id,
                        ProductFields.slug,
                        ProductFields.category().fields(CategoryFields.id),
                    )
                ),
            ),
            Query.products(first=10, channel="default-channel").alias("my_products").fields(
                ProductCountableConnectionFields.edges().fields(
                    ProductCountableEdgeFields.node().fields(
                        ProductFields.id,
                        ProductFields.slug,
                    )
                ),
            )
        ]
        result = await saleor_client.query(
            *query_str,
            operation_name="getProducts",
        )
        result_json = json.dumps(result.json())

query_str:

query getProducts { 
    products(channel: "default-channel", first: 1) { 
        edges { 
            node { 
                id 
                slug 
                category { 
                    id 
                } 
            } 
        } 
    } 
    my_products: products(channel: "default-channel", first: 10) { 
        edges { 
            node { 
                id 
                slug 
            } 
        } 
    } 
}