fix: dev: Try to skip lock on fully lower names

fix: dev: Try to skip lock on fully lower names

If the name is fully lowercase, we don't need to access the case bitmap in order to set the case. Therefore, we can check for the FULLYLOWERCASE flag using only atomic operations, and skip a lock in the hot path, provided we clear the FULLYLOWERCASE flag before changing the case bitmap.

Merge branch 'alessio/skip-lock-on-fully-lower-names' into 'main'

See merge request isc-projects/bind9!10497