DEFAULT_HOST_DEPTH_LIMIT: This limit applies to the host environment. It
guards recursion paths involving the Env and Budget, particularly
during operations like conversion, comparison, and deep cloning. The limit
is strategically checked at critical recursion points, such as when
encountering a Val. As the actual stack usage can be higher,
DEFAULT_HOST_DEPTH_LIMIT is conservatively set to a lower value than the
XDR limit.