Blockless LLM module integration

[zees-dev]

Summary of Changes

Introducing Blockless LLM integration for the SDK.
This allows SDK consumer to integrate with host runtime LLM module and interact with it.
Currently only setting the model (via model-name) and prompting the model is supported.

FFI interface to call into host LLM module:

#[link(wasm_import_module = "blockless_llm")]
extern "C" {
    fn llm_set_model_request(model_ptr: *const u8, model_len: u32, fd: *mut u32) -> i32;
    fn llm_get_model_response(buf: *mut u8, size: u32, num: *mut u32, fd: u32) -> i32;
    fn llm_set_model_options_request(options_ptr: *const u8, options_len: u32, fd: u32) -> i32;
    fn llm_get_model_options(buf: *mut u8, size: u32, num: *mut u32, fd: u32) -> i32;
    fn llm_prompt_request(prompt_ptr: *const u8, prompt_len: u32, fd: u32) -> i32;
    fn llm_read_prompt_response(buf: *mut u8, size: u32, num: *mut u32, fd: u32) -> i32;
    fn llm_close(fd: u32) -> i32;
}

An example has been included which demonstrates how to interact with two different LLM models.

Note: The LLM module only works in the browser runtime.