feat: add narrow shared memory accessor to UninitializedSandbox

Signed-off-by: danbugs <danilochiarlone@gmail.com>

Author: danbugs

src/hyperlight_host/src/sandbox/uninitialized.rs

@@ -161,6 +161,11 @@ impl<'a> From<GuestBinary<'a>> for GuestEnvironment<'a, '_> {
 }
 
 impl UninitializedSandbox {
+    /// Returns a mutable reference to the sandbox's shared memory region.
+    pub fn shared_mem_mut(&mut self) -> &mut ExclusiveSharedMemory {
+        &mut self.mgr.shared_mem
+    }
+
     // Creates a new uninitialized sandbox from a pre-built snapshot.
     // Note that since memory configuration is part of the snapshot the only configuration
     // that can be changed (from the original snapshot) is the configuration defines the behaviour of