fix: backport, divide stdout and stderr from helm to not create corrupted outputs

[renzodavid9]

Fixes: #8327

Description
This PR is to backport a v2 fix: using skaffold render with a helm deployer, with helm >= 3.10.2, pulling from an OCI registry is generating a corrupted yaml output, so here we are setting two different buffers, one for stdout and another for stderr to split the messages and differentiate between the generated yaml content and the errors.

Related PRs from v2

• fix: helm template warnings breaking yaml parsing #7825
• fix: stderr of "helm template" not printed #7986
• fix: not print error message if it is empty #8005

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[renzodavid9]

How to reproduce the issue

Environment

• You need helm >= 3.10.2
• You need an OCI registry. One easy way to get one running in your local machine is with Docker Registry. You only need to run:

docker run -d -p 5000:5000 --name registry registry:2

Upload a chart to your local OCI registry

• You can create one from examples/helm-deployment. In the folder run:

helm package ./charts/

• It will create a .tgz file. Upload that file to your local registry:

helm push ./skaffold-helm-0.1.0.tgz oci://localhost:5000/helm-charts

Reproduce the issue

• Using skaffold v1.39.4, create a project with the following skaffold.yaml file:

apiVersion: skaffold/v2beta28
kind: Config

metadata:
  name: chart-in-oci

deploy:
  helm:
    releases:
    - name: oci-test
      remoteChart: oci://localhost:5000/helm-charts/skaffold-helm

• Run skaffold render --output=render.yaml
• Open the generated render.yaml file, you'll see at the beginning of the file the content that is breaking the file:

Pulled: localhost:5000/helm-charts/skaffold-helm:0.1.0
Digest: sha256:8ba9820...

Solve the issue

• Download the PR
• Build a new skaffold version
• Run skaffold render --output=render.yaml
• Open the generated render.yaml file, you'll see there is no extra content

[aaron-prindle]

LGTM - Confirmed manually that this is working for me as well via the repro steps provided. Awesome!