Fix 9280 - func_num_args() presence must not allow unlimited args

[mvorisek]

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[ondrejmirtes]

Thank you, but I've already said in the issue: phpstan/phpstan#9280

This has been in PHPStan for a long time and there might be users relying on opposite behaviour than you want. I'm not willing to change it.
You can adjust your code not to use func_num_args instead.

[mvorisek]

I would really like to get this merged as func_num_args has legit uses on non-variadic methods. The tests also shows no big BC-break will be introduced, actually there is no single BC-break. If the variadic args are retrived using func_get_arg or func_get_args, which is typical for variadic functions with undeclared params, everything is analysed as before.

[mvorisek]

@ondrejmirtes the E2E tests show no single issue, I have done a short brainstorming and with this PR I do not see any, even minor downside, using func_num_args without retriving the actual args (via func_get_arg/func_get_args) does not make much sense. Ondřej, what usecase do you have in your head?

The problem with the current (before this PR) behaviour is a lot of problems can be supressed and this is probably also the reason why noone reported it yet.