Update object keys of `Dimensions` to match new spec about dbt-semantic-interfaces HOT 2 CLOSED

@QMalcolm looking at this now, I'm wondering if we (I) missed is_partition in the RFC 🤔 . From the documentation & code, this doesn't look to be doing anything that we wouldn't want it to do in the new implementation.

I would propose that we amend the discussion to include is_partition and include it in the new spec. That would mean that the only property that would need to be removed would be Metadata as it will be implemented in dbt-core with meta.

from dbt-semantic-interfaces.

The only other one that I think would need to change would be removing time_format from DimensionTypeParams. It appears that it was primarily used for legacy support (as inferred by comment?). The only places it is used in the codebase is in the dimension class and then in tests.

class DimensionTypeParams(HashableBaseModel):
    """Dimension type params add additional context to some types (time) of dimensions"""

    is_primary: bool = False
    # For legacy support. This is not used.
    time_format: str = ISO8601_FMT
    time_granularity: TimeGranularity
    validity_params: Optional[DimensionValidityParams] = None

from dbt-semantic-interfaces.