Support Incremental Unmanaged in Native

[eakmanrq]

This would allow users to do append only inserts. We want to make sure in documentation that we recommend users explore other incremental models before using unmanaged.

[sungchun12]

What are clear examples where you recommend this?

[dmat]

This is a wonderful feature and meets my use case. I'm building a Data Vault based Datawarehouse, and one of the fundamental principles is to insert only operations for auditability and scalability. Can't wait for this feature. One recommendation is the ability to do controlled restatement and new snapshots for breaking changes.

[djayatillake]

Why couldn't you do this with incremental by time already?

[izeigerman]

Let's also enable restatements by default for this model kind while we're at it.

[erindru]

This PR exposes the existing INCREMENTAL_UNMANAGED model kind to native projects.

However, im still not sure it will meet the need. What do you mean by a "controlled restatement"? Currently, it's set to "full history restatement only" which means it will be rebuilt from scratch if you attempt to restate a portion of it.

[dmat]

Full history restatement is good, ty.