The memcpy in HEX2BUF was copying the length of the buffer that was
passed in, not the actual length of the converted hexstring. This
test was segfaulting in the Alpine CI which uses clang/musl.
Add a test to show the incorrect ASN1 conversion to and from points.
This was due to the check if Y is odd/even being inverted which
incorrectly prefixes the X coordinate with the wrong byte.
The test itself was not fully correct because it was using compliant
points rather than full points, and the spec contains the entire
Y coordinate so the full point should be used.
This patch also adds ASN1 conversions to validate that
dpp_point_from_asn1 and dpp_point_to_asn1 work properly.
