feat(kernel): add Kernel struct, MockPlatform, and simple syscalls (GetTime, GetProcessId, Yield)

crates/types/src/time.rs

@@ -2,6 +2,14 @@
 pub struct Ticks(u64);
 
 impl Ticks {
+    pub fn from_raw(value: u64) -> Self {
+        Self(value)
+    }
+
+    pub fn raw(&self) -> u64 {
+        self.0
+    }
+
     pub fn elapsed_since(&self, earlier: &Ticks) -> Ticks {
         Ticks(self.0.saturating_sub(earlier.0))
     }