Refactors v2 codec handling

[normanrz]

This PR refactors the handling of codecs for v2 arrays by introducing a new private V2Codec class instead of V2Filters and V2Compressor. It just applies the filters/codecs in order without caring about buffer types.

closes #2325

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/tutorial.rst
• Changes documented in docs/release.rst
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[mpiannucci]

Chiming in to say that I tested this with existing kerchunk stores and it works great!