[php-src] Issue #23423: php_embed_ub_write does not return on error

Issue: https://github.com/php/php-src/issues/23423
Author: Sjord

### Description

sapi/embed/php_embed.c:

```
/* SAPIs only have unbuffered write operations. This is because PHP's output
 * buffering feature will handle any buffering of the output and invoke the
 * SAPI unbuffered write operation when it flushes the buffer.
 */
static size_t php_embed_ub_write(const char *str, size_t str_length)
{
	const char *ptr = str;
	size_t remaining = str_length;
	size_t ret;

	while (remaining > 0) {
		ret = php_embed_single_write(ptr, remaining);
		if (!ret) {
			php_handle_aborted_connection();
		}
		ptr += ret;
		remaining -= ret;
	}

	return str_length;
}
```

`php_handle_aborted_connection` does not always abort, i.e. if `ignore_user_abort=1`. So I sending fails and `ret` is 0, then `remaining` is never decremented and this loops forever.

It should probably `return str_length - remaining` after `php_handle_aborted_connection()`.

### PHP Version

```plain
master
```

### Operating System

_No response_