Update base for Update on "Pass one NDM to backend init"

Take external NDM if it exists, otherwise internal.

Note: by default, xnnpack uses the named_data_map. Constants are not stored with the delegated blob anymore.

Differential Revision: [D73679710](https://our.internmc.facebook.com/intern/diff/D73679710/)

[ghstack-poisoned]

Author: lucylq