[CT-3013] [Bug] non_additive_dimension property window_groupings should be optional but isn't

[QMalcolm]

Is this a new bug in dbt-core?

• I believe this is a new bug in dbt-core
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

Currently if you specify a measure with a non_additive_dimension that doesn't have a window_groupings property you get an error. The work around is to specify an empty list, i.e. window_groupings: []

Expected Behavior

No error should be raised if window_groupings isn't specified

Steps To Reproduce

1. Add a non_additive_dimension measure to a semantic model

semantic_models
  - name: your_semantic_model
  ...
  measures:
    - name: test_non_additive
       agg: sum
       expr: lifetime_spend_pretax
       non_additive_dimension:
         name: first_ordered_at
         window_choice: max

2. Run dbt parse
3. Get an error like the following

16:02:24  Encountered an error:
Parsing Error
  Invalid semantic_models config given in FilePath(searched_path='models', relative_path='marts/customers.yml', modification_time=1691182373.747098, project_root='/Users/quigleymalcolm/Developer/dbt-labs/jaffle-sl-template') @ semantic_models: {'name': 'your_semantic_model, 'defaults': {'agg_time_dimension': 'first_ordered_at'}, 'description': 'Customer grain mart.\n', 'model': "ref('customers')", 'entities': [{'name': 'customer', 'expr': 'customer_id', 'type': 'primary'}], 'dimensions': [{'name': 'customer_name', 'type': 'categorical'}, {'name': 'customer_type', 'type': 'categorical'}, {'name': 'first_ordered_at', 'type': 'time', 'type_params': {'time_granularity': 'day'}}, {'name': 'last_ordered_at', 'type': 'time', 'type_params': {'time_granularity': 'day'}}], 'measures': [{'name': 'count_lifetime_orders', 'description': 'Total count of orders per customer.', 'agg': 'sum'}, {'name': 'lifetime_spend_pretax', 'description': 'Customer lifetime spend before taxes.', 'agg': 'sum'}, {'name': 'lifetime_spend', 'agg': 'sum', 'description': 'Gross customer lifetime spend inclusive of taxes.'}, {'name': 'test_non_additive', 'agg': 'sum', 'expr': 'lifetime_spend_pretax', 'non_additive_dimension': {'name': 'customer_type', 'window_choice': 'max'}}]} - at path ['measures'][3]['non_additive_dimension']: {'name': 'customer_type', 'window_choice': 'max'} is not valid under any of the given schemas

Relevant log output

See above

Environment

- OS: macOS Ventura 13.4.1
- Python: 3.8.10
- dbt: 1.6.0

Which database adapter are you using with dbt?

snowflake

Additional Context

No response