refactor(kernel): move SyscallOutcome/Result to syscall module, move test helpers to tests module

crates/kernel/src/syscall/capability.rs

@@ -1,6 +1,7 @@
 use platform::Platform;
 
-use crate::{Kernel, SyscallOutcome, SyscallResult};
+use super::{SyscallOutcome, SyscallResult};
+use crate::Kernel;
 
 impl<P: Platform> Kernel<P> {
     pub(crate) fn handle_delegate(

crates/kernel/src/syscall/ipc.rs

@@ -1,6 +1,7 @@
 use platform::Platform;
 
-use crate::{Kernel, SyscallOutcome, SyscallResult};
+use super::{SyscallOutcome, SyscallResult};
+use crate::Kernel;
 
 impl<P: Platform> Kernel<P> {
     pub(crate) fn handle_send(

crates/kernel/src/syscall/lifecycle.rs

@@ -1,6 +1,7 @@
 use platform::Platform;
 
-use crate::{Kernel, SyscallOutcome, SyscallResult};
+use super::{SyscallOutcome, SyscallResult};
+use crate::Kernel;
 
 impl<P: Platform> Kernel<P> {
     pub(crate) fn handle_spawn_thread(

crates/kernel/src/syscall/memory.rs

@@ -1,6 +1,7 @@
 use platform::Platform;
 
-use crate::{Kernel, SyscallOutcome, SyscallResult};
+use super::{SyscallOutcome, SyscallResult};
+use crate::Kernel;
 
 impl<P: Platform> Kernel<P> {
     pub(crate) fn handle_request_pages(

crates/kernel/src/syscall/mod.rs

@@ -4,10 +4,27 @@ mod lifecycle;
 mod memory;
 mod simple;
 
-use domain::syscall::Syscall;
+use domain::{error::KernelError, message::Message, syscall::Syscall};
 use platform::Platform;
+use types::{bounded::CapSlot, id::ThreadId};
 
-use crate::{Kernel, SyscallOutcome, SyscallResult};
+use crate::Kernel;
+
+pub enum SyscallOutcome {
+    Complete(SyscallResult),
+    BlockCaller(domain::thread::BlockReason),
+    SwitchTo(ThreadId),
+    TerminateCaller,
+}
+
+pub enum SyscallResult {
+    Ok,
+    Value(usize),
+    Slot(CapSlot),
+    Message(Message),
+    WakeReason(domain::syscall::WakeReason),
+    Error(KernelError),
+}
 
 impl<P: Platform> Kernel<P> {
     pub fn handle_syscall(&mut self, syscall: Syscall) -> SyscallOutcome {

crates/kernel/src/syscall/simple.rs

@@ -1,6 +1,7 @@
 use platform::Platform;
 
-use crate::{Kernel, SyscallOutcome, SyscallResult};
+use super::{SyscallOutcome, SyscallResult};
+use crate::Kernel;
 
 impl<P: Platform> Kernel<P> {
     pub(crate) fn handle_get_time(&self) -> SyscallOutcome {