Maintain compatibility with pre Hudi 0.9.0 config keys, while marking them as deprecated

With introduced a new configuration framework in HUDI-89, where all the String configurations have been replaced with ConfigProperty structure.

However, we still want to maintain compatibility with existing pre Hudi 0.9.0 config keys, so that it does not break existing users. At the same time, we will mark the previous config keys as deprecated so users can start migrating to the new configs.