cmake: WITH_SYSTEM_UTF8PROC defaults to OFF

cmake: WITH_SYSTEM_UTF8PROC defaults to OFF

change the default value of WITH_SYSTEM_UTF8PROC from ON to OFF, so that
centos/rhel users can build with the default cmake configuration. no other
WITH_SYSTEM_* variable in ceph defaults to ON, so this is consistent
with other bundled libraries like boost and rocksdb

unfortunately, this also means that users that do have system packages
must opt-in to using them with -DWITH_SYSTEM_UTF8PROC=ON

both deb and rpm builds dependended on the previous default value, so
their logic was negated to match the new default

Fixes: https://tracker.ceph.com/issues/55114
Signed-off-by: Casey Bodley <cbodley@redhat.com>