Partial duckdb index
For big datasets, instead of using all the parquet files, use only the first ones until the limit of 5GB is reached.
It's used for both `search` and `filter`.

## Indexing

I added three fields in the duckdb-index job:
- partial (if it used a partial parquet export or if it didn't index the full parquet export)
- num_rows
- num_bytes

## New jobs

I also added two jobs and their responses can be used in the front-end instead of the `size` endpoint:
- config-duckdb-index-size
- dataset-duckdb-index-size

Both jobs return the same response format as the config-size and the dataset-size jobs, but with information about the size of the indexed data instead of the size of the parquet-exported data.

## Update of search and filter

I also added the `partial` field in the responses of `/search` and `/filter`, in case they use a partial index.

## Index file

The file name is `index.duckdb` if it indexes all the rows from the parquet export, otherwise it's named `partial-duckdb.index`. It is placed in the same folder as the parquet export in `refs/convert/parquet`.

Fix https://github.com/huggingface/datasets-server/issues/1742

TODO
- [x] tests
- [x] docs
- [x] openapi
- [x] update /search and /filter for partial indexes
Partial duckdb index: For big datasets, instead of using all the parquet files, use only the first ones until the limit of 5GB is reached.
It's used for both `search` and `filter`.

## Indexing

I added three fields in the duckdb-index job:
- partial (if it used a partial parquet export or if it didn't index the full parquet export)
- num_rows
- num_bytes

## New jobs

I also added two jobs and their responses can be used in the front-end instead of the `size` endpoint:
- config-duckdb-index-size
- dataset-duckdb-index-size

Both jobs return the same response format as the config-size and the dataset-size jobs, but with information about the size of the indexed data instead of the size of the parquet-exported data.

## Update of search and filter

I also added the `partial` field in the responses of `/search` and `/filter`, in case they use a partial index.

## Index file

The file name is `index.duckdb` if it indexes all the rows from the parquet export, otherwise it's named `partial-duckdb.index`. It is placed in the same folder as the parquet export in `refs/convert/parquet`.

Fix https://github.com/huggingface/datasets-server/issues/1742

TODO
- [x] tests
- [x] docs
- [x] openapi
- [x] update /search and /filter for partial indexes