Enhancement: Slim down minimum required dependencies

[provinzkraut]

Summary

Ideally we want the base litestar package to have as few dependencies as possible. Right now we install a lot of extra packages that aren't actually needed for the core functionality.
These fall roughly into two groups: Speedups and additional features.

Speedups include:

• fast-query-parsers (fix: don't implicitly parse URL encoded form data as JSON #2394)
• multidict

Additional features:

• pyyaml to support exporting the OpenAPI schema as YAML
• httpx for the TestClient
• polyfactory to generate OpenAPI examples (feat(OpenAPI): lazy import example creator #2390)

Libraries required for Litestar to work

• anyio
• msgspec

The goal would be to exclude everything that's not strictly necessary from the base install and make it available through package extras, which could be included in the standard extra as well. This is a common practice and is used by packages like uvicorn, starlette and fastapi.

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The plan is to work on these without breaking anything, and removing the packages as required dependencies once we hit 3.0.

Basic Example

No response

Drawbacks and Impact

No response

Unresolved questions

No response

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[hyperknot]

I find it a bit strange that fast-query-parsers is included only with [standard], but standard also includes jinja2.

But jinja2 is quite bloated and makes no sense for a JSON API (the typical use case of litestar I guess), so installing standard is not a good idea if you only need a JSON API. But then fast-query-parsers has to be installed manually.

Currently, I'm installing it via:

litestar[sqlalchemy,cli] 
fast-query-parsers

[JacobCoffee]

Some more data in #2844