Auto collect tuple responses schema references

[juhaku]

Refactor Tuple responses parsing unifying it with request body parsing. This allows reusing same components when serialized to tokens making it less error prone and removing duplication.

This also removes the content_type = [...] array format from ToResponse and IntoResponses derive types as well as from tuple style responses. Same as with request bodies the multiple content types need to defined with content(...) attribute.

Implement auto collect response schema references from tuple style responses within #[utoipa::path(...)] attribute macro. Schema references will be collected recursively in same manner as for request bodies.

Breaking

The content_type = [...] array format is no longer supported. And instead content(...) is to be used instead for defining multiple content types.

Example of supported syntax. The User will be automatically collected to OpenApi when get_user path is registered to the OpenApi.

 #[derive(utoipa::ToSchema)]
 struct User {
     name: String,
 }

 #[utoipa::path(
     get,
     path = "/user",
     responses(
         (status = 200, body = User)
     )
 )]
 fn get_user() {}

Closes #1065 Closes #1025 Closes #465