new: usr: Add manual mode configuration option to dnsec-policy

Add a new option ``manual-mode`` to :any:`dnssec-policy`. The intended use is that if it is enabled, it will not automatically move to the
next state transition, but instead the transition is logged. Only after manual confirmation with ``rndc dnssec -step`` the transition is made.

Closes #4606

Merge branch '4606-dnssec-policy-dry-run' into 'main'

See merge request isc-projects/bind9!10774