fix(Core): guard SysvProcessor message size and handle oversized messages in BatchJob

[cy-yun]

Fixes #9394

Problem

When kernel.msgmax is raised above the standard default of 8192 bytes (e.g. kernel.msgmax = 65536 in containerized or high-throughput environments), SysvProcessor::submit()'s initial call to msg_send(..., self::$typeDirect, $item) succeeds for serialized items between 8193 and msgmax bytes.

However, BatchJob::run() calls msg_receive($q, 0, $type, 8192, $message, true, 0, $errorcode) with a hardcoded buffer limit of 8192 bytes and without MSG_NOERROR. Under System V IPC msgrcv(2), when a message in the queue exceeds msgsz and MSG_NOERROR is not set in msgflg, the syscall fails with E2BIG ($errorcode === 7 / PCNTL_E2BIG), leaving the message unconsumed at the head of the queue. Because the queue is not empty, subsequent msg_receive calls return immediately with E2BIG, causing a 100% CPU busy-loop and indefinitely blocking all subsequent messages.

Solution

1. SysvProcessor:
   • Added const MAX_DIRECT_SIZE = 8192.
   • Before attempting msg_send(..., self::$typeDirect, ...), check if strlen($serialized) <= self::MAX_DIRECT_SIZE.
   • If the serialized item exceeds 8192 bytes, immediately invoke the temporary file fallback (self::$typeFile) instead of pushing an oversized direct message to the queue, reusing $serialized and ensuring direct messages never exceed 8192 bytes.
2. BatchJob:
   • Added const MAX_MESSAGE_SIZE = 8192.
   • In run(), when msg_receive fails with E2BIG (checked against PCNTL_E2BIG, SOCKET_E2BIG, MSG_E2BIG, or POSIX errno 7), drain the poison message via drainOversizedMessage($q) using MSG_IPC_NOWAIT | MSG_NOERROR without unserializing. This consumes and purges the poison message from the queue head, preventing CPU starvation.
3. Tests & Style Compliance:
   • Added boundary test cases in SysvProcessorTest::items() for items exceeding 8192 bytes.
   • Added unit tests in BatchJobTest for isMsgTooBig() and drainOversizedMessage().
   • Verified that all unit tests in Core/tests/Unit pass (537 tests, 856 assertions, 100% pass).
   • Validated code style with php-tools cs-fixer (Found 0 of 471 files that can be fixed) and phpcs (0 errors, 0 warnings).