Function parse_aws_chunk_header 

pub fn parse_aws_chunk_header(buf: &[u8]) -> Option<(usize, usize)>

Parse one aws-chunked frame header from buf.

The aws-chunked format is:

<hex-payload-size>;chunk-signature=<sig>\r\n<payload>\r\n

Returns Some((header_len, payload_len)) when a complete header is available, or None if more data is needed.

header_len is the number of bytes occupied by the header line (including the trailing \r\n). payload_len is the number of payload bytes that follow.