[FEA] Improve download and extract utility

[ryantwolf]

Errors when incorrectly using the download and extraction utilities are hard to debug, and the purpose of download and extraction can be unclear.

Describe the solution you'd like
For download_common_crawl when snapshot numbers are invalid we get this error:

Traceback (most recent call last):
  File "/workspace/NeMo-Curator/examples/download_common_crawl.py", line 53, in <module>
    main(attach_args().parse_args())
  File "/workspace/NeMo-Curator/examples/download_common_crawl.py", line 35, in main
    common_crawl = download_common_crawl(
  File "/usr/local/lib/python3.10/dist-packages/nemo_curator/download/commoncrawl.py", line 342, in download_common_crawl
    dataset = download_and_extract(
  File "/usr/local/lib/python3.10/dist-packages/nemo_curator/download/doc_builder.py", line 185, in download_and_extract
    df = dd.from_map(
  File "/usr/local/lib/python3.10/dist-packages/dask/dataframe/io/io.py", line 992, in from_map
    raise ValueError("All `iterables` must have a non-zero length")

We should do the following:

• Update the documentation to explicitly call out that the snapshot numbers must be valid
• Provide a link to the list of valid snapshots in the documentation.
• Catch this error and rethrow an error with a more informative error message.

Furthermore, we should clarify the purpose of the download_and_extract utility. Users should not be under the impression that NeMo Curator does web crawling. We can optionally provide a simple download and extraction utility that operates on raw urls.