[Feature] Add Behavior Change for legacy time spine configuration

[DevonFulcher]

Is this your first time submitting a feature request?

• I have read the expectations for open source contributors
• I have searched the existing issues, and I could not find an existing issue for this feature
• I am requesting a straightforward extension of existing dbt functionality, rather than a Big Idea better suited to a discussion

Describe the feature

The configuration for MetricFlow time spines has been updated to be part of the yaml spec https://docs.getdbt.com/docs/build/metricflow-time-spine. A behavior change should be added so that users are informed of the deprecation.

Describe alternatives you've considered

No response

Who will this benefit?

This will benefit MetricFlow users.

Are you interested in contributing this feature?

Yes.

Anything else?

No response