fix: dev: Remove unneeded options in dns_zonefetch

In the `dns_zonefetch` mechanism, some option flags for
`dns_resolver_createfetch()` were used for all fetches, but
were actually only needed by the `DNSKEY` refresh fetches.

(Specifially, these options were `DNS_FETCHOPT_UNSHARED`
and `DNS_FETCHOPT_NOCACHED`, which were used along with
`DNS_FETCHOPT_NOVALIDATE` to ensure we get a new copy of
the DNSKEY as it is currently published by the authority,
without prior validation.  Those conditions are needed
for RFC 5011 trust anchor maintenace, but not when looking
up parent-`NS` or `DSYNC` RRsets.)

Merge branch 'each-zonefetch-cleanup' into 'main'

See merge request isc-projects/bind9!11866