Add fallback type on get_type when handling DataType.ARRAY

[justmatias]

Change summary

• Increased test coverage for the get_type utility in the standard generator.
• Added explicit tests for handling OpenAPI array types, including the fallback to typing.Any when the items property is missing from the schema.
• Added tests to verify correct list[T] generation.

Related issue(s)

#207

Pull request tasks

The following have been completed for this task:

• Code changes
• Tests written
• Documentation changes for new or changed features
• Pre-review preparation
  • make test
  • make format
  • make ty
  • make generate-test-clients
    • Test clients have changed because a new feature was introduced
    • Test clients remain the same
• Changelog updated
• Contributors updated

[justmatias]

@phalt I've noticed that this was never merged. It's possible to merge it.
Feel free to do so if you still think it's a good fix :).

[phalt]

@justmatias hello sorry, honest answer is I just forgot! Life got in the way.