Expose config to disable upsert behavior

[blampe]

This exposes opt-in provider configuration to disable upsert behavior. When this is set we will use CSA for creation and surface "already exists" errors when we attempt to overwrite something.

I called the config enableUpsert to be consistent with some of our other configs (although I'd prefer disableUpsert since that makes it more obvious what the default behavior is).

An E2E test is included and I'll try to add some units around this as well.

Fixes https://github.com/pulumi/pulumi-kubernetes/issues/2926.

[github-actions[bot]]

Does the PR have any schema changes?

Looking good! No breaking changes found. No new resources/functions.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 11.76471% with 30 lines in your changes are missing coverage. Please review.

Project coverage is 29.79%. Comparing base (09be004) to head (0006ded).

Files	Patch %	Lines
provider/pkg/gen/schema.go	0.00%	21 Missing :warning:
provider/pkg/provider/provider.go	25.00%	7 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3000      +/-   ##
==========================================
- Coverage   29.86%   29.79%   -0.08%     
==========================================
  Files          63       63              
  Lines        8353     8384      +31     
==========================================
+ Hits         2495     2498       +3     
- Misses       5634     5660      +26     
- Partials      224      226       +2     

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[EronWright]

Let me state my opinion here, that Kubernetes SSA is designed for a multi-party authoring experience (where multiple parties apply their intentions to a given object), but design-wise says nothing about object lifecycle. For example, it doesn't answer the question of "who should delete this object, my party or your party?". An auto-scaler, for example, would not expect to create or to delete a given object, merely to control the replicas field while the object exists.

Pulumi has features like "import" and "retainOnDelete" to control an object's lifecycle, and there's no good reason that SSA should complicate that, in my opinion. I agree with disabling upsert, perhaps opt-in in v4 and always disabled in v5.