Add DateInterval extension

[VincentLanglet]

Follow up of the discussion 181f75c#r50600099

I try to add some ThrowTypeExtension. This one seems easy.

The others in https://github.com/pepakriz/phpstan-exception-rules/tree/master/src/Extension are

• DOMDocumentExtension: This one is half-wrong. It makes the code believe method can throw an ErrorException but I discover it only throw a Warning and the error handler is transforming this to ErrorException when using APP_DEBUG=true with Symfony. Still, empty string will throw an error in PHP8.
  http://sandbox.onlinephpfunctions.com/code/9a26ff8a86809b4e9848d9635ec0debeee36e355.

• IntdivExtension

• JsonEncodeDecodeExtension

• ReflectionExtension

• SimpleXMLElementExtension

• SplFileObjectExtension

I'll try to add more after this PR.
First I'd like to understand something @ondrejmirtes. When I'm returning

return $methodReflection->getThrowType();

I assume this rely on the fact that the exception which can be thrown by the method is well documented. Where can I check if it is ? Do you rely on Phpstorm stubs ?

Does it means for instance that intdiv is not considered as throwing an exception because the phpdoc does not contains throws tag ?

/**
 * Integer division
 * @link https://php.net/manual/en/function.intdiv.php
 * @param int $num1 <p>Number to be divided.</p>
 * @param int $num2 <p>Number which divides the <b><i>dividend</i></b></p>
 * @return int <p>
 * If divisor is 0, a {@link DivisionByZeroError} exception is thrown.
 * If the <b><i>dividend</i></b> is <b>PHP_INT_MIN</b> and the <b><i>divisor</i></b> is -1,
 * then an {@link ArithmeticError} exception is thrown.
 * </p>
 * @since 7.0
 */
#[Pure]
function intdiv ($num1, $num2) {}

[ondrejmirtes]

return $methodReflection->getThrowType();

This will return the type from @throws above method declaration. Yes, if phpstorm-stubs have it then it will returned. Please note that stub files from /stubs have priority over phpstorm-stubs.

Does it means for instance that intdiv is not considered as throwing an exception because

Missing @throws can either mean that it will not throw anything, or that it can throw anything. See: https://phpstan.org/blog/bring-your-exceptions-under-control#what-does-absent-%40throws-above-a-function-mean%3F

See also this commit: 09d3488

[ondrejmirtes]

Thank you!