EVP_PKEY_asn1_find_str() would search through standard asn1 methods
first, then those added by the application, which EVP_PKEY_asn1_find()
worked the other way around.  Also, EVP_PKEY_asn1_find_str() didn't
handle aliases.

This change brings EVP_PKEY_asn1_find_str() closer to EVP_PKEY_asn1_find().

Fixes #5086
Reviewed-by: NBernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/5137)