Cldfzenodo

- Make `version_tag` argument to `from_concept_doi` optional, to make it more transparent
that this is the method to call to get the latest version for a concept DOI.

- Add Python 3.12 to supported versions.
- Added API method to retrieve release information from GitHub/Zenodo.

Zenodo's upgrade from Oct. 13, 2023 brought a couple of breaking changes for the Zenodo API.
While it was possible to accomodate these changes in the implementation of `cldfzenodo`, while
keeping the **cldfzenodo** API as is, we took the opportunity to also add a streamlined API. This
only affects the `cldfzenodo` Python API, though - the commandline interface
`cldfbench zenodo.download`, as well as the `DatasetResolver` functionality has not
changed. The old Python API is still available, though, but using it will trigger deprecation
warnings.

Deprecated functionality will be removed in v2.2.


Other changes

- Dropped py3.7 compatibility.

- Added support for retrieval of versioned datasets via concept DOI and version tag.
- Added support for downloading full deposits via CLI.

First feature-complete release