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

Commit `2956e4fc` hardened the `key` name check when used in `primaries` to reject the configuration if the key was not defined, rather than simply checking whether the key name was correctly formed.

However, the key name check didn't include the view configuration, causing keys not to be recognized if they were defined inside the view and not at the global level.  This regression is now fixed.

Backport of MR !11588

Closes #5761

Merge branch 'backport-5761-key-view-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11613