Fix resource drop functionality in worker-executor - #717

[afsalthaj]

Fix #717

There were a couple of scenarios here:

• The group1 integration test uses forwarding.rs which skips validation with metadata, and the result of a drop invoke is unused. To be precise, use of let _ = . This led to diverging behaviour between invokes through worker-service and worker-executor
• Worker-Executor stored the result in oplog (when a resource is dropped) as an empty array.
• During dropping the resource, executor expects the input parameter to be a Value::Handle however, the input json has to be a serde_json::Value::String (which indirectly represented a resource) resulting in executor failure
• All of the above scenario is handled in this PR.
• Note that such a wrong expectation of wasm_rpc::Value resulted in infinite loop, which is no more the case after this fix. So I definitely think this has to go in

This fix will unblock #660