fix: resolve issue where kubectl Flags.Apply namespace flag usage would fail

[aaron-prindle]

fixes #8336

Adding that issue text inline below:

There is currently an issue where skaffold apply uses incorrect namespace if kubectl -n or --namespace flag is provided in deploy.kubectl.flags.apply field

Repro:

skaffold.yaml

apiVersion: skaffold/v4beta1
kind: Config
build:
  tagPolicy:
    gitCommit: {}
  local: {}
manifests:
  rawYaml:
  - /workspace/source/deployment.yaml
  - /workspace/source/service.yaml
  - /workspace/source/httproute.yaml
deploy:
  kubectl:
    flags:
      apply:
      - --namespace=service-mesh
  logs:
    prefix: container

manifests.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: service-mesh
  name: service-mesh-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: service-mesh
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: service-mesh
    spec:
      containers:
      - image: gcr.io/google-containers/nginx:latest
        imagePullPolicy: Always
        name: hello-app

Unexpected/Bug-indicating Error message (should work):

- the namespace from the provided object "default" does not match the namespace "service-mesh". You must pass '--namespace=default' to perform this operation.

Works with:

    flags:
      global:
      - --namespace=service-mesh

But not:

    flags:
      apply:
      - --namespace=service-mesh

[codecov]

Codecov Report

Merging #8351 (7a6ab5d) into main (290280e) will decrease coverage by 4.61%.
The diff coverage is 54.85%.

@@            Coverage Diff             @@
##             main    #8351      +/-   ##
==========================================
- Coverage   70.48%   65.88%   -4.61%     
==========================================
  Files         515      605      +90     
  Lines       23150    29786    +6636     
==========================================
+ Hits        16317    19624    +3307     
- Misses       5776     8686    +2910     
- Partials     1057     1476     +419     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/completion.go	13.04% <0.00%> (-1.25%)	⬇️
cmd/skaffold/app/cmd/config/list.go	65.21% <ø> (ø)
cmd/skaffold/app/cmd/config/set.go	88.72% <ø> (ø)
cmd/skaffold/app/cmd/config/util.go	54.28% <ø> (ø)
cmd/skaffold/app/cmd/credits.go	100.00% <ø> (ø)
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/generate_pipeline.go	60.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_modules.go	65.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_profiles.go	66.66% <ø> (ø)
... and 415 more

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