feat(server-framework): add Server trait, Encode/Decode, async executor, syscall wrappers, and mock arch for host testing

crates/server-framework/src/async_syscall/mod.rs

@@ -0,0 +1,15 @@
+pub async fn send(endpoint: usize, w0: usize, w1: usize, w2: usize, w3: usize) -> usize {
+    userspace::syscall::send(endpoint, w0, w1, w2, w3)
+}
+
+pub async fn receive(endpoint: usize) -> (usize, usize, usize, usize) {
+    userspace::syscall::receive(endpoint)
+}
+
+pub async fn wait_for_interrupt(irq: usize) {
+    userspace::syscall::yield_now();
+}
+
+pub async fn acknowledge_interrupt(irq: usize) {
+    let _ = irq;
+}