Remove extra leading '00:' when printing key material with highest byte >= 0x80

Remove extra leading '00:' when printing key material with highest byte >= 0x80

Removed pseudo-DER encoding of (unsigned) BNs from output of ASN1_bn_print() and
print_labeled_bignum() in providers/implementations/encode_decode/encode_key2text.c
Also adapt test output reference files where needed.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8136)