A SigV4-compatible signer for S3 service. In order to support SigV4a algorithm according to the operation input
dynamically, the signer wraps native module SigV4a signer and JS SigV4 signer. It signs the request with SigV4a
algorithm if the request needs to be signed with
* region. Otherwise, it signs the request with normal SigV4
Note that SigV4a signer is only supported in Node.js now because it depends on a native dependency.