ref(cells): send cell_name on the wire

[lynnagara]

the pydantic models RpcOrganizationMapping and RpcOrganizationMappingUpdate used for rpc now send cell_name instead of region_name on the wire

support for both fields was added in #111039

[markstory]

Looking at this locally, we'll still be sending region_name on the wire after these changes.

>>> from sentry.hybridcloud.services.organization_mapping.model import RpcOrganizationMappingUpdate
>>> r = RpcOrganizationMappingUpdate(cell_name='us', customer_id=None, name="test", status=0, slug="test")
>>> r.dict()
{'name': 'test', 'status': 0, 'slug': 'test', 'region_name': 'us', 'customer_id': None, 'requires_2fa': False, 'early_adopter': False, 'codecov_access': False, 'disable_shared_issues': False, 'allow_joinleave': False, 'disable_new_visibility_features': False, 'enhanced_privacy': False, 'require_email_verification': False, 'disable_member_project_creation': False, 'prevent_superuser_access': False, 'disable_member_invite': False}

I think for cell_name to be used on the wire format, the models would need a formal cell_name attribute.

[markstory]

We could also override the dict() method to copy region_name into cell_name so that both fields are present in the wire data.

[lynnagara]

oh i see, updated the models so cell_name is default and region_name is accepted and co-erced into cell_name instead of the other way around

this is deploy safe since both are currently valid now, just flipping the default