hello_world need to get updated

[KaranocaVe]

1. The current default cmake configuration file causes "gemma/gemma.h" and several other header files to be missing.
2. Attempting to use the deleted constructor gcpp::NestedPools::NestedPools(gcpp::NestedPools &&) and gcpp::Gemma::Gemma(const gcpp::Gemma &)
3. gcpp::RuntimeConfig runtime_config has problem, because the definition changed.

[KaranocaVe]

#649 I have already resolved the issue in this PR.

[Balakrishna-Chennamsetti]

Hi @KaranocaVe ,

Thank you so much for your contribution to Gemma open source models, really appreciated on that. Once the PR is merged please feel free to close the issue thread.

Thanks.