Refactor: add const qualifiers for (de)compression

- Updated `compress_chunk` function to use `const` qualifiers for `chunk` and `chunk_model` parameters to ensure data integrity
- Updated `decompress_cmp_entiy` function to use `const` qualifiers for `ent` and `model_of_data` parameters to ensure data integrity
- Renamed `input_buf` to `src` and `icu_output_buf` to `dst` and `buffer_length` to `stream_size` for clarity