ChainLoader constructor should accept iterable instead of array

[TheCelavi]

Closes #4200

[stof]

ah indeed. Supporting lazy-loaded iterators would require making the ChainLoader configuration immutable instead of having this addLoader. So let's forget it...

[TheCelavi]

There is also this method which can be used to preserve lazy loading:

    public function addLoader(LoaderInterface $loader): void
    {
        $existing = $this->loaders;

        $this->loaders = static function () use ($existing, $loader): \Generator {
            yield from $existing;
            yield $loader;
        };

        $this->hasSourceCache = [];
    }

I don't think that it would have much of the performance impact when adding 5-10 loaders (hardly real-world scenario, people usually use 1-2 loaders and that is it).

Are you more interested in this method? @stof

[xabbuh]

We could deprecate addLoader() in 3.x and introduce lazy loading in Twig 4.

[TheCelavi]

I have updated PR with modification which will support preserving lazy loading of loaders with addLoaders() method.

[fabpot]

Thank you @TheCelavi.