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.
The current implementation of remote attestation does not take into
account the integrity of the wasm module. The SHA256 of the wasm
module has been put into user_data to generate the quote, and more
parameters are exposed for further verification.
