Add streaming decompression for ZSTD_CONTENTSIZE_UNKNOWN case

[mkitti]

Zstandard can use a streaming compression scheme where the total size of the data is not known at the beginning of the process. In this case, the size of the data is unknown
and is not saved in the Zstandard frame header.

Before this pull request, numcodecs would refuse to decompress data if the size were unknown. This pull request adds a routine to decompress data if the size is unknown,
specifically when ZSTD_getFrameContentSize returns ZSTD_CONTENTSIZE_UNKNOWN.

This pull request is based on prior pull request I made to numcodecs.js:
manzt/numcodecs.js#47

Fixes zarr-developers/zarr-python#2056

xref:
zarr-developers/zarr-python#2056

This is currently a draft.

TODO:

• Unit tests and/or doctests in docstrings
• Tests pass locally
• Docstrings and API docs for any new/modified user-facing classes and functions
• Changes documented in docs/release.rst
• Docs build locally
• GitHub Actions CI passes
• Test coverage to 100% (Codecov passes)