add support for converting traditional hive tables to iceberg/delta/hudi

### Feature Request / Improvement

there are a lot of systems that produce parquet files only, it will be useful if xtable can convert those parquet to modern tables formats without rewriting data just by adding metadata continuously.

Delta do that already but it is a one off operation and can't accept new files

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

No files, tests, or entry points are named. Start by reading XTable's existing conversion flow and its handling of Parquet inputs and metadata-only updates; define the design for continuously converting new files into Iceberg, Delta, or Hudi tables without rewriting data, then verify the behavior across the requested table formats.

Written by the indexing model from the issue text.