Stop calling Request::get on Symfony 7.4 / 8.0 as it is deprecated

[ruudk]

Description

Since Symfony 7.4 (released a few weeks ago) calling get on Request is deprecated, see: https://symfony.com/blog/new-in-symfony-7-4-request-class-improvements#deprecated-the-get-method

But it seems that New Relic is calling this a lot, see:

newrelic-php-agent/agent/fw_symfony4.c

Lines 175 to 178 in f69754b

	request, "Symfony\\Component\\HttpFoundation\\Request" TSRMLS_CC)) {
	/* Let's look for _route first. */
	zval* route_rval
	= nr_symfony_object_get_string(request, "_route" TSRMLS_CC);

newrelic-php-agent/agent/fw_symfony4.c

Lines 190 to 191 in f69754b

	zval* controller_rval
	= nr_symfony_object_get_string(request, "_controller" TSRMLS_CC);

Both these cases should be replaced with $request->attributes->get

[ruudk]

Since get is removed from Request, calling it on Symfony 8 will no longer work.