fix: Helm deploy was not working with variable templatinging chart path

[travishein]

I believe the chartPath property is supposed to be a templatable field.

In my use I have helm charts in a separate git repo from the application where the skaffold.yaml is. We defined a skaffold.env.template file, that we add to git and then on checkout we copy this to skaffold.env and modify as needed, so the path to the location to the other repo with a helm chart is a variable. and this skaffold.env file is added to the .gitignore

We noticed that we were getting
listing files: issue walking releases: lstat {{.HELM_REPO}}/helm/app/chart/path: no such file or directory

This PR fixes this issue.

Fixes: #nnn
Related: Relevant tracking issues, for context
Merge before/after: Dependent or prerequisite PRs

Description

User facing changes (remove if N/A)

Follow-up Work (remove if N/A)

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[code-review-assist]

Hi team,

I'm currently reviewing this pull request and will provide a full review shortly. In the meantime, here's a quick summary for you and other reviewers to get up to speed:

This pull request, submitted by @travishein, addresses an issue where Helm deployments were failing when using variable templating for the chartPath property. The problem stemmed from the chartPath not being correctly interpreted as a template, leading to errors like lstat {{.HELM_REPO}}/helm/app/chart/path: no such file or directory.

Intent: The primary goal is to enable the use of environment variables within the chartPath setting for Helm deployments, allowing for more flexible chart location management.

Changes:

The core change involves modifying the helm.go file (specifically lines 398-408). The original code directly used the release.ChartPath value, which was not being templated. The updated code now uses util.ExpandEnvTemplateOrFail to expand any environment variables present in release.ChartPath before using it to locate the Helm chart. This ensures that the path is correctly resolved, even if it's defined using variables from a skaffold.env file.

Summary Table:

File	Change Summary
pkg/skaffold/deploy/helm/helm.go	Added environment variable expansion to release.ChartPath before path traversal.

I'll provide a more detailed review shortly, including a check for potential edge cases and thorough testing.

---

And now, a little haiku to lighten the mood:

Paths once unclear,
Now templated, bright and bold,
Skaffold builds anew.

[code-review-assist]

This change correctly addresses the issue of the chartPath not being templatable by expanding the environment variable. The implementation is good, but a couple of minor suggestions for improved readability and a potential performance enhancement are included below.