Refactor dmod.modeldata serialization and deserialization types

[aaraney]

This PR refactors dmod.modeldata's dmod.core.serializable.Serializable subtypes into compliance with the changes introduced in #239. These changes should not affect downstream usage of dmod.modeldata Serializable subtypes.

For broader context, implications, and examples regarding changes that affect the Serializable subtype, see #239.

Changes

• Serialization, deserialization, validation, and type coercion are now mainly handled by pydantic. All subtypes of dmod.core.serializable.Serializable are affected by this change.
• pydantic added as dmod.modeldata dependency
• missing dependency, GitPython, added to dmod.modeldata's setup.py

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

[aaraney]

In writing some tests to accompany this PR I stumbled into a question. Is the below the desired behavior, @robertbartel?

from dmod.modeldata.hydrofabric.partition import Partition, PartitionConfig

catchment_ids = ["1", "2", "3"]
partition_id = 0

o1 = Partition(
        partition_id=partition_id,
        catchment_ids=catchment_ids,

        nexus_ids=["2"],
        remote_up_nexuses=["1"],
        remote_down_nexuses=["3"],
        )

o2 = Partition(
        partition_id=partition_id,
        catchment_ids=catchment_ids,

        nexus_ids=["2222"],
        remote_up_nexuses=["1111"],
        remote_down_nexuses=["3333"]
        )

same_catchment_id_and_partition_id = PartitionConfig(partitions=[o1, o2])

assert len(same_catchment_id_and_partition_id.partitions) ==  1

[aaraney]

Thanks, @robertbartel!