[llava][20/N] Add llava runner using building blocks in e/llm/runner (#4666)

* [llava][18/N] Move token generation loop to a class

As titled. This PR moves the token generation loop in llama2 runner into
a new class so it can be reused.

[ghstack-poisoned]

* [llava][19/N] Add multimodal runner base class and build file

[ghstack-poisoned]

* [llava][20/N] Add llava runner using building blocks in e/llm/runner

[ghstack-poisoned]

* Update base for Update on "[llava][20/N] Add llava runner using building blocks in e/llm/runner"


Add llava runner that uses runner lib in `extension/llm/runner`.


[ghstack-poisoned]

* Update base for Update on "[llava][20/N] Add llava runner using building blocks in e/llm/runner"


Add llava runner that uses runner lib in `extension/llm/runner`.

Differential Revision: [D61292846](https://our.internmc.facebook.com/intern/diff/D61292846)

[ghstack-poisoned]