[9.20] chg: dev: replace #define DNS_GETDB_ with struct of bools
requested to merge backport-4559-convert-dns_getdb_x-defines-to-1-bit-long-bools-9.20 into bind-9.20
Replace #define DNS_GETDB_ with struct of bools to make it easier to pretty-print the attributes in a debugger.
Closes #4559 (closed)
Backport of MR !9093 (merged)