Update base for Update on "[Executorch][llm] Enable local global attention in export_llama script"

Added a new option of --local_global_attention that takes in pattern of sizes to determine which layers are using local sliding window attention.
For example, [0, 256, 256, 0, 256, 256] can be used for 6 layers transformer. Or you can also use [0, 256, 256] as pattern you want
to repeat.

Differential Revision: [D73891423](https://our.internmc.facebook.com/intern/diff/D73891423/)

cc larryliu0820 mergennachin cccclai helunwencser jackzhxng

[ghstack-poisoned]

Author: kimishpatel