🌵 Olive kv_cache_config under io_config

[trajepl]

Describe your changes

1. Add the option of kv_cache_config in io_config:
   • kv_cache_config: None or False, will not enable kv cache
   • kv_cahce_config: True or dict, will generate related kv_cache input based on existed io_config and model attributes.
     • Suggest to set True for huggingface transformer models
     • Suggest to set dict for non-huggingface models
2. Update phi2/llama2 example by removing io_config/dummy_inputs_func from user_scirpts and config json.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.
• Is this PR including examples changes? If yes, please remember to update example documentation in a follow-up PR.

(Optional) Issue link

[guotuofeng]

Better allow specify the kv cache if user would like keep using io_config function.

fix comments