Block fields' defaults are not filled in the forms when creating new block doc

[ahuang11]

    type: Literal["bigquery"] = Field(default="bigquery")
    test_int: int = Field(default=200)

it’s in BigQueryTargetConfigs.schema()

 'properties': {'extras': {'title': 'Extras', 'type': 'object'},
  'type': {'title': 'Type',
   'default': 'bigquery',

[pleek91]

Related to https://github.com/PrefectHQ/orion-design/issues/476