ext/soap: Fix SOAP classmap validation for integer keys

[LamentXU123]

Previously, SOAP only rejected packed arrays, which still allowed sparse integer-keyed arrays and mixed string integer-keyed arrays to be accepted.

Since classmap is expected to be an associative mapping, arrays containing integer keys are now rejected consistently.

[devnexen]

could you add the following test please ?

--TEST--
SoapClient must not read a packed "classmap" array as a hash
--EXTENSIONS--
soap
--FILE--
<?php

class LocalClient extends SoapClient
{
    public function __doRequest(string $request, string $location, string $action, int $version, bool $oneWay = false, ?string $uriParserClass = null): ?string
    {
        echo $request, PHP_EOL;

        return <<<XML
        <?xml version="1.0" encoding="UTF-8"?>
        <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
          <SOAP-ENV:Body><ns1:doItResponse xmlns:ns1="urn:test"/></SOAP-ENV:Body>
        </SOAP-ENV:Envelope>
        XML;
    }
}

$client = new LocalClient(null, [
    'location' => 'http://example.com/',
    'uri' => 'urn:test',
    'classmap' => ['SomeType' => 'stdClass'],
]);

$property = new ReflectionProperty(SoapClient::class, '_classmap');
$property->setValue($client, ['stdClass', 'stdClass']);

$client->__soapCall('doIt', [new stdClass()]);

echo 'done', PHP_EOL;

?>
--EXPECTF--
%A
done

[LamentXU123]

This is indeed a bug when SoapClient::_classmap can be reflected as a packed array :)