[HttpKernel] Support variadic with #[MapRequestPayload]

[DjordyKoert]

Q	A
Branch?	7.2
Bug fix?	no
New feature?	yes
Deprecations?	no
Issues	-
License	MIT

Adds support for variadic arguments in combination with #[MapRequestPayload].

Example request

Content-Type: application/json
[
    {"price": 50},
    {"price": 23}
]

Example controller usage

class MyController
{
    public function __invoke(
        #[MapRequestPayload] Price ...$prices,
    ): Response {
        // do something with $prices -> array<Price>
    }
}

This PR also fixes a bug introduced in #49978 where using #[MapUploadedFile] with a variadic argument causes a TypeError:

class MyController
{
    public function __invoke(
        #[MapUploadedFile] UploadedFile ...$documents,
    ): Response {
    }
}

Argument #1 must be of type Symfony\\Component\\HttpFoundation\\File\\UploadedFile, array given

[carsonbot]

Hey!

I see that this is your first PR. That is great! Welcome!

Symfony has a contribution guide which I suggest you to read.

In short:

• Always add tests
• Keep backward compatibility (see https://symfony.com/bc).
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• Features and deprecations must be submitted against the 7.1 branch.

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Carsonbot