Fix crash when a timed invoke happens for a large payload command. (project-chip#38622)

Because we don't pass the exchange through command handling, treating it as
out-of-band state instead, we have to maintain that state on all codepaths that
can lead to command handling.

Also fixes timed writes, but those are not exercised right now.

Fixes project-chip#38580

Author: bzbarsky-apple

src/app/InteractionModelEngine.cpp

@@ -1929,6 +1929,9 @@ void InteractionModelEngine::OnTimedInvoke(TimedHandler * apTimedHandler, Messag
     VerifyOrDie(aPayloadHeader.HasMessageType(MsgType::InvokeCommandRequest));
     VerifyOrDie(!apExchangeContext->IsGroupExchangeContext());
 
+    // Ensure that DataModel::Provider has access to the exchange the message was received on.
+    CurrentExchangeValueScope scopedExchangeContext(*this, apExchangeContext);
+
     Status status = OnInvokeCommandRequest(apExchangeContext, aPayloadHeader, std::move(aPayload), /* aIsTimedInvoke = */ true);
     if (status != Status::Success)
     {
@@ -1949,6 +1952,9 @@ void InteractionModelEngine::OnTimedWrite(TimedHandler * apTimedHandler, Messagi
     VerifyOrDie(aPayloadHeader.HasMessageType(MsgType::WriteRequest));
     VerifyOrDie(!apExchangeContext->IsGroupExchangeContext());
 
+    // Ensure that DataModel::Provider has access to the exchange the message was received on.
+    CurrentExchangeValueScope scopedExchangeContext(*this, apExchangeContext);
+
     Status status = OnWriteRequest(apExchangeContext, aPayloadHeader, std::move(aPayload), /* aIsTimedWrite = */ true);
     if (status != Status::Success)
     {