Migrate ome_model Python package to its own repository

[sbesson]

The code under https://github.com/ome/ome-model/tree/v6.3.6/ome_model has had little maintenance/development over the last 4 years.
Functionally, its content is also very different from the rest of this code base which contains:

1- the source XSD files for the OME data model
2- sample XML files for the different schema versions
3- the code-generated Java implementation of the OME model objects

Following the extraction to a separate repository, a decision should likely be made with regard to maintaining it vs archiving it in favor of other community Python projects like https://pypi.org/project/ome-types/.

Originally posted by @sbesson in #193 (review)

[joshmoore]

Especially if we feel comfortable that our existing scripts could be re-written on top of ome-types, I'd be 👍 trying to unify on it.

[sbesson]

Agreed, as a proof of concept, I worked on a minimal example upgrading a IDR script generating an HCS companion file using this package to ome-types.

The code difference is very reasonable - see IDR/idr0092-ostrop-organoid#2 and the generated OME-XML is consistent with the original one with the only differences being related to attribute ordering and UUIDs.

Based on this minimal investigation, I am further inclined to remove this project and deprecate it in favor of ome-types. At the API level, I cannot see anything that I would care about maintaining. If any was raised as valuable, I would propose to discuss how to open it as a contribution against ome-types directly. Any valuable experience gained from this project could be also be converted into documentation https://ome-types.readthedocs.io/.