[php-src] Issue #23978: PHP_STREAM_OPTION_READ_TIMEOUT is also used for socket write timeouts

Issue: https://github.com/php/php-src/issues/23978 Author: matyhtf ### Description stream_set_timeout() passes PHP_STREAM_OPTION_READ_TIMEOUT to the stream wrapper: https://github.com/php/php-src/blob/810ac6dc4d2bb5b74f0a9ba478f4b9202f68cb10/ext/standard/streamsfuncs.c#L1494-L1499 The constant and its comment explicitly describe a read timeout: https://github.com/php/php-src/blob/810ac6dc4d2bb5b74f0a9ba478f4b9202f68cb10/main/php_streams.h#L448-L450 However, the native socket stream stores this option in the single sock->timeout field: https://github.com/php/php-src/blob/810ac6dc4d2bb5b74f0a9ba478f4b9202f68cb10/main/streams/xp_socket.c#L407-L410 That timeout is used by both php_sockop_read() and php_sockop_write(). In particular, a blocking write which encounters EAGAIN/EWOULDBLOCK waits for POLLOUT using the same timeout: https://github.com/php/php-src/blob/810ac6dc4d2bb5b74f0a9ba478f4b9202f68cb10/main/streams/xp_socket.c#L65-L128 This creates an ambiguity for extension and alternative stream-wrapper implementers: following the constant name and header comment produces a read-only implementation, while matching native PHP socket stream behavior requires applying the value to both blocking reads and blocking writes. This ambiguity caused a real compatibility issue in Swoole's coroutine stream hook, where stream_set_timeout() changed the read timeout but a blocked fwrite() continued using the previous write timeout: https://github.com/swoole/swoole-src/pull/6260 The PHP manual currently says only that the function “sets the timeout value on the stream”; it does not document that native network/socket streams use the value for writes as well, and its example demonstrates only a read timeout: https://github.com/php/doc-en/blob/master/reference/stream/functions/stream-set-timeout.xml Suggested changes: 1. Clarify the stream_set_timeout() documentation: for native network/socket streams, the configured timeout applies to blocking reads and blocking writes. 2. Update the misleading comment in main/php_streams.h. 3. Introduce a direction-neutral internal name such as PHP_STREAM_OPTION_IO_TIMEOUT or PHP_STREAM_OPTION_TIMEOUT, while retaining PHP_STREAM_OPTION_READ_TIMEOUT as an alias for source compatibility, and migrate in-tree users to the clearer name. 4. Consider adding a php-src regression test covering a blocked socket-stream write after stream_set_timeout(). No runtime behavior change is being requested here; the goal is to make the existing behavior unambiguous and prevent downstream implementations from interpreting the option differently.