Fix DiffSuppressFunc for databricks_model_serving resource

[nkvuong]

Changes

Closes #2811

Tests

• make test run locally
• covered with integration tests in internal/acceptance
• relevant acceptance tests are passing
• using Go SDK

[alexott]

But with the Default, do we really need a suppress diff?

[nkvuong]

@alexott the problem is on Azure, where GPU serving is not enabled, the API returns empty workload_type...

[alexott]

and yeah, then we'll have GCP

[nkvuong]

integration tests passed

[mgyucht]

@nkvuong can we do the following instead:

			common.MustSchemaPath(m, "config", "served_models", "workload_type").Computed = true
			common.MustSchemaPath(m, "config", "served_models", "workload_type").Optional = true

That way, if the user doesn't specify, we fall back to the API default (which could be empty, as in Azure), and if they remove the value, it would keep its original value. I'm just so confused by DiffSuppressFunc... I'm going to try to repro now and use this change.

[mgyucht]

We can move forward with this as-is. I think we need to revisit how we use Computed/Optional vs DiffSuppressFunc in the future; in the meantime, let's just add a comment here, and merge.

[codecov-commenter]

Codecov Report

Merging #2813 (95c6cf1) into master (9f3658d) will decrease coverage by 0.10%.
Report is 8 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2813      +/-   ##
==========================================
- Coverage   84.75%   84.65%   -0.10%     
==========================================
  Files         150      151       +1     
  Lines       13086    13145      +59     
==========================================
+ Hits        11091    11128      +37     
- Misses       1394     1411      +17     
- Partials      601      606       +5     

Files	Coverage Δ
serving/resource_model_serving.go	80.76% <100.00%> (+1.13%)	⬆️

... and 7 files with indirect coverage changes