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.

core/iwasm/common/wasm_runtime_common.c

@@ -1160,6 +1160,12 @@ wasm_runtime_deinstantiate(WASMModuleInstanceCommon *module_inst)
     wasm_runtime_deinstantiate_internal(module_inst, false);
 }
 
+WASMModuleCommon *
+wasm_runtime_get_module(WASMModuleInstanceCommon *module_inst)
+{
+    return (WASMModuleCommon *)((WASMModuleInstance *)module_inst)->module;
+}
+
 WASMExecEnv *
 wasm_runtime_create_exec_env(WASMModuleInstanceCommon *module_inst,
                              uint32 stack_size)