fix: usr: Resolve "key defined in view is not found"

A recent change in `2956e4fc45b3c2142a3351682d4200647448f193` hardened the `key` name check when used in `primaries` to immediately reject the configuration if the key was not defined (rather than only checking whether the key name was correctly formed). However, the change introduced a regression that prevented the use of a `key` defined in a view. This is now fixed.

Merge branch '5761-key-view' into 'main'

See merge request isc-projects/bind9!11588