* Sigv4a implementation

Co-authored-by: Michael Graeb <graebm@amazon.com>
Co-authored-by: Bret Ambrose <bambrose@amazon.com>
Co-authored-by: rccarper <51676630+rccarper@users.noreply.github.com>
Co-authored-by: Andrew Tang <tangliang551@gmail.com>
Co-authored-by: Pushen Wang <wps132230@hotmail.com>
Co-authored-by: Dengke Tang <dengket@amazon.com>