[Sync-EN] Document the SOAP PHP 8.4 changes

[lacatoire]

Syncs the five reference/soap/ pages with php/doc-en#5735 and php/doc-en#5699.

php/doc-en#5735:

• SoapClient::$typemap is typed array|null instead of resource|null, and its description, which was an empty paragraph, explains what it holds and that code checking it with is_resource() needs updating for PHP 8.4.0.
• SoapClient::__construct() and SoapServer::__construct(): the classmap option documents the Clark notation keys, {namespace}type, added in PHP 8.4.0 for mapping a type from a specific XML namespace.
• SoapServer::setPersistence() gains a changelog section: as of 8.4.0 SOAP_PERSISTENCE_SESSION works with a shared session extension, where it previously failed silently, and the method throws an Error when that constant is requested while the session extension is unavailable.
• SoapVar::__construct() gains the 8.4.0 row about a DateTimeInterface value for an xsd:dateTime element now serializing to its ISO 8601 representation instead of an empty string.

php/doc-en#5699: mirrors the removal of the two empty xi:fallback elements in the SoapClient synopsis.

EN-Revision bumped to d20d66d9c76ff98dceb853aeb86794fe9d657669 on the five files.

Fixes: #1623