compute version field in Check, use 3-way diff

[EronWright]

Proposed changes

This PR stabilizes Helm upgrades by abandoning the use of checksums (which was added in v4.5.0, see PR), while allowing for local chart change detection via the chart's version number. That is, the user is now expected to touch the chart's version to compel Pulumi to roll out the change.

Implementation-wise, this is accomplished by resolving the version property during Check. The checked input reflects the goal version, and if the goal has changed, then Diff detects this in the natural way and effects an upgrade. Check no longer uses helm template to render the chart, it simply resolves the chart version.

The diff logic is improved here to use a three-way merge, to be able to detect drift in the actual Helm release.

The refresh logic is improved to not mutate inputs (as was done in the past to help with drift detection).

Demonstration

This video clip demonstrates:

1. An initial deployment using the current version of the provider.
2. A repro of the issue that Pulumi sees a spurious change to checksum.
3. Upon building the new provider, the spurious change is gone because the checksum property is gone and the diff logic for version property compares new input to old state.
4. Upon a change to the local chart's version, Pulumi sees a change to version.
5. Drift detection, by using helm upgrade and then pulumi refresh such that Pulumi sees the change.

Note that the demo app doesn't set the version property, it relies on the new logic in Check to resolve the version.

issue-2649-low.mov

Summary of Old/New Behavior

Old:

Action	Op	Raw Input	Checked	Old (Input)	Old (State)	New (State)
Deploy 3.47.1	Check	~3.47.0	~3.47.0	-	-	-
	Create	-	~3.47.0	-	-	3.47.1
Upgrade to 3.47.2	Check	~3.47.0	~3.47.0	-	-	-
	Diff	-	~3.47.0	~3.47.0	3.47.1	-
	Update	-	-	-	-	-
Drift to 3.47.3	Read	-	3.47.3	-	-	3.47.3
	Check	~3.47.0	~3.47.0	3.47.3	-	-
	Diff	-	~3.47.0	3.47.3	3.47.3	-

New:

Action	Op	Raw Input	Checked	Old (Input)	Old (State)	New (State)
Deploy 3.47.1	Check	~3.47.0	3.47.1	-	-	-
	Create	-	3.47.1	-	-	3.47.1
Upgrade to 3.47.2	Check	~3.47.0	3.47.2	-	-	-
	Diff	-	3.47.2	3.47.1	3.47.1	-
	Update	-	3.47.2	3.47.1	3.47.1	3.47.2
Drift to 3.47.3	Read	-	3.47.2	-	-	3.47.3
	Check	~3.47.0	3.47.2	3.47.2	-	-
	Diff	-	3.47.2	3.47.2	3.47.3	-

Related issues (optional)

Closes #2649

[github-actions]

Does the PR have any schema changes?

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

[codecov]

Codecov Report

Attention: 49 lines in your changes are missing coverage. Please review.

Comparison is base (9078fd3) 18.52% compared to head (5545d9b) 18.42%.

Files	Patch %	Lines
provider/pkg/provider/helm_release.go	0.00%	49 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2672      +/-   ##
==========================================
- Coverage   18.52%   18.42%   -0.11%     
==========================================
  Files          47       47              
  Lines        9643     9587      -56     
==========================================
- Hits         1786     1766      -20     
+ Misses       7753     7722      -31     
+ Partials      104       99       -5     

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[rquitales]

LGTM