refactor: remove vestiges of parsing release info text from helm deployment

[briandealwis]

This PR is a minor refactoring of the Helm post-deployment parsing to reflect the reality after #5723.

Prior to #5723, our Helm deployer would invoke helm get all <chart> to obtain the deployed manifests. This output some semi-structured text with release information, followed by the manifests. We discarded the release info and then parsed out the remaining YAML. But this could fail (#5484) as there was no clean separation between the release info and the YAML.

example showing output from `helm get all skaffold-helm`

$ helm get all skaffold-helm -n namespace
NAME: skaffold-helm
LAST DEPLOYED: Fri Nov 26 12:59:05 2021
NAMESPACE: namespace
STATUS: deployed
REVISION: 1
TEST SUITE: None
USER-SUPPLIED VALUES:
null

COMPUTED VALUES:
image: skaffold-helm:latest
replicaCount: 2

HOOKS:
MANIFEST:
apiVersion: apps/v1
kind: Deployment
metadata:
[...elided...]

Since we don't actually use the Helm release info text, #5723 changed our deployer to instead use helm get all <chart> --template {{.Release.Manifest}} to only output the Kubernetes manifests. But there were some vestiges of the release-info parsing still present.

This PR removes the last bits of this release-info parsing. In so doing, I discovered that our tests weren't providing an actual deployed manifest to helm get all, and so the namespaces were not being properly reported, and so our deploy-with-namespace tests weren't actually checking that the right namespaces were being reported!

[codecov]

Codecov Report

Merging #6913 (09ee40e) into main (290280e) will decrease coverage by 1.34%.
The diff coverage is 61.83%.

@@            Coverage Diff             @@
##             main    #6913      +/-   ##
==========================================
- Coverage   70.48%   69.14%   -1.35%     
==========================================
  Files         515      547      +32     
  Lines       23150    25080    +1930     
==========================================
+ Hits        16317    17341    +1024     
- Misses       5776     6575     +799     
- Partials     1057     1164     +107     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/deploy.go	52.00% <ø> (-1.85%)	⬇️
cmd/skaffold/app/cmd/dev.go	84.61% <0.00%> (ø)
cmd/skaffold/app/cmd/flags.go	91.00% <0.00%> (+0.18%)	⬆️
cmd/skaffold/app/cmd/render.go	36.66% <0.00%> (-4.72%)	⬇️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/fix.go	68.85% <40.00%> (-7.62%)	⬇️
cmd/skaffold/app/cmd/lint.go	42.85% <42.85%> (ø)
cmd/skaffold/app/cmd/find_configs.go	48.88% <50.00%> (+0.24%)	⬆️
cmd/skaffold/app/skaffold.go	76.19% <70.00%> (-8.43%)	⬇️
... and 164 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6e95e61...09ee40e. Read the comment docs.

[MarlonGamez]

LGTM