Qualcomm AI Engine Direct - Support kv_cached stories 110M llama2 (#4142)

Summary:
- Add custom memory descirptor
- Add e2e example script verified with story110M in 8a8w, 16a4w
- Add qnn_llama_runner to run static LLAMA.
- Add readme
- Add slice op test
- Change RemoveClone to RemoveRedundancy
- Change SimpleADB parameter artifact to build_path and related codes
- Change multihead attentions to multiple single head.
- Move sort inputs from execute to init
- Remove split op
- Support u16 and u8 mixed-precision quantization.

Pull Request resolved: https://github.com/pytorch/executorch/pull/4142

Reviewed By: kirklandsign

Differential Revision: D59339823

Pulled By: cccclai

fbshipit-source-id: 51fcf14e406b04c51de6e421cccbad91a8ffa01e