Adopt new(x) over ptr.To(x) and re-enable newexpr lint

Replace all ptr.To(x) calls with the Go 1.26 built-in new(x), remove
the newexpr suppression from .golangci.yml, and drop unused
k8s.io/utils/ptr imports. Also fix two pre-existing modernize lint
issues (stringsbuilder, atomic).

Signed-off-by: Kunal Memane <kmemane@redhat.com>