Adds a new QA test to cover chula_buffer_encode_md5_digest()
Adds a new QA test to cover chula_buffer_encode_md5_digest()

alobbs/libhpack,alobbs/libhpack,http2d/core,http2d/core,alobbs/libhpack,http2d/core,alobbs/libhpack,http2d/core