Create module hash for each module in SGX lib-rats (#1745)

Current SGX lib-rats wasm module hash is stored in a global buffer,
which may be overwritten if there are multiple wasm module loadings.
We move the module hash into the enclave module to resolve the issue.

And rename the SGX_IPFS macro/variable in Makefile and Enclave.edl to
make the code more consistent.

And refine the sgx-ra sample document.

product-mini/platforms/linux-sgx/enclave-sample/App/App.cpp

@@ -103,7 +103,7 @@ enclave_init(sgx_enclave_id_t *p_eid)
                <= MAX_PATH - 1 - sizeof(TOKEN_FILENAME) - strlen("/")) {
         /* compose the token path */
         strncpy(token_path, home_dir, MAX_PATH);
-        strncat(token_path, "/", strlen("/"));
+        strncat(token_path, "/", strlen("/") + 1);
         strncat(token_path, TOKEN_FILENAME, sizeof(TOKEN_FILENAME) + 1);
     }
     else {