implement generic I/O async request object to replace file-specific async requests, refactor lwIP network stack to dispatch requests through IRPs with cancellation support, add cancellation polling to lwIP accept and receive operations using LwipSocketWaitRecvNetbuf and LwipSocketWaitAccept, introduce NetSubmitSocketIrp for routing socket operations via device IRPs, track network IRP statistics with SYS_NET_IRP_STATS, add process module lock spinlock and reference counting for process modules, implement dynamic module loading and unloading via user module handles, add POSIX dynamic loader APIs including dlopen, dlsym, dlerror, and dlclose, introduce PosixStart entry point for posix applications, add new native smoke tests for net IRPs.

code/user/runtime/posix_start.c

@@ -0,0 +1,13 @@
+// POSIX process startup. This file owns process-local POSIX personality initialization before main runs.
+
+extern int main(void);
+extern void exit(int status);
+extern void PosixFdInit(void);
+
+// Initializes POSIX process state and exits with main's return value.
+void PosixStart(void) {
+    PosixFdInit();
+    int status = main();
+    exit(status);
+    for (;;) {}
+}