Return wildcard names instead of synthetized names in dns_db_find()

Return wildcard names instead of synthetized names in dns_db_find()

Previously dns_db_find() would return the synthetized name on a
wildcard match. This is insufficient, as sometimes query processing
requires the wildcard name instead of the synthetized name.

This commit modifies the dns_db_find() API to return the wildcard
name instead of the synthetized name, and adds helper functions to
query.c to derive the synthetized name if needed.