InnerFunctionsSniff should flag functions defined inside closures

InnerFunctionsSniff detects functions defined inside other functions, but not inside closures, meaning it won't report any violations for the following snippet:

```php
$myFunc = function () {
	function test(): int {
		return 54;
	}
};
```

For consistency, this should be treated the same as:

```php
function myFunc() {
	function test(): int {
		return 54;
	}
}
```