Dynamic Modules Fixed Per Direction Continue Flags

Fixed a bug in the HTTP filter where the decode and encode directions shared a single continue flag, so a request body that continued the decode direction while an upstream response was held at encodeHeaders turned the later continueEncoding() into a silent no-op and wedged the held response. Because the flag was shared, one resume could never continue both directions. The decode and encode continue states are now tracked independently so a continue in one direction never suppresses a resume in the other.