tests(unit): Add llm-enhanced-test submodule integration

[kylo5aby]

No description provided.

[lum1n0us]

CMake Error at CMakeLists.txt:93 (add_subdirectory):
  The source directory

    /home/runner/work/wasm-micro-runtime/wasm-micro-runtime/tests/unit/llm-enhanced-test

  does not contain a CMakeLists.txt file.

might want to add some cases into the llm-enhanced-test repo to make CI happy(may also need to change CI and let me know if you need help), or not include those cases until everything is set up in the llm-enhanced-test repo.