DCAP deployment improvement

[henrysun007]

Motivation & problem statement

The deployment for DCAP attestation is not well supported. runtime.config.toml and build.config.toml have to be modified manually. There are three runtime.config.tomls in config, docker and tests/fixtures respectively.

[henrysun007]

Besides, there are many issues about the attestation:
#667
#634
#548
#469
#459
#452

More documents are needed about the attestation. The attesation also needs improvement.

[hiroki-chen]

Hi @henrysun007, I noticed that the port for attestation is hardcoded as 443 in attestation/src/service.rs:

let addrs = url.socket_addrs(|| match url.scheme() {
    "https" => Some(443), // Fixed port.
    _ => None,
})?;

Is it possible for us to change the binding port? Sometimes 443 on the local machine is already in use for other services so that we cannot deploy DCAP.