Allow overriding portworx target namespace

[an-toine]

Make sure to have done the following:

• Signed off your work as per the DCO.
• Add unit-tests

What this PR does / why we need it:
This PR adds a new namespaceOverride value to the Portworx chart so that user can easily override the target Portworx install namespace.

Which issue(s) this PR fixes (optional)
#728

Special notes for your reviewer:
My specific unit-test is passing but diffs are reported around image tags which I believe are not related to my changes :

root@f21272600cc8:/app/test/portworx# go test -run TestStorageClusterHelmTemplate/TestOverrideNamespace
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: Running command helm with args [template -f /app/test/portworx/testValues/storagecluster_override_namespace.yaml --show-only templates/storage-cluster.yaml my-release /app/charts/portworx]
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: ---
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: # Source: portworx/templates/storage-cluster.yaml
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: kind: StorageCluster
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: apiVersion: core.libopenstorage.org/v1
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: metadata:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   name: "mycluster"
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   namespace: custom-namespace
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   annotations:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   labels:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     heritage: "Helm"
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     release: "my-release"
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     chart: "portworx-5.1.3"
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     app.kubernetes.io/managed-by: "Helm"
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     app.kubernetes.io/instance: "my-release"
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66: spec:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   image: portworx/oci-monitor:3.2.2
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   imagePullPolicy: Always
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   kvdb:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     internal: true
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   storage:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     useAll: true
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   secretsProvider: k8s
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   stork:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     enabled: true
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   monitoring:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     telemetry:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:       enabled: true
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   csi:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     enabled: true
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:   autopilot:
TestStorageClusterHelmTemplate/TestOverrideNamespace 2025-03-27T10:23:43Z logger.go:66:     enabled: true
Differences found:
  map[string]any{
        "apiVersion": string("core.libopenstorage.org/v1"),
        "kind":       string("StorageCluster"),
        "metadata":   map[string]any{"annotations": nil, "labels": map[string]any{"app.kubernetes.io/instance": string("my-release"), "app.kubernetes.io/managed-by": string("Helm"), "heritage": string("Helm"), "release": string("my-release")}, "name": string("mycluster"), "namespace": string("custom-namespace")},
        "spec": map[string]any{
                "autopilot":       map[string]any{"enabled": bool(true)},
                "csi":             map[string]any{"enabled": bool(true)},
-               "image":           string("portworx/oci-monitor:3.2.1.1"),
+               "image":           string("portworx/oci-monitor:3.2.2"),
                "imagePullPolicy": string("Always"),
                "kvdb":            map[string]any{"internal": bool(true)},
                ... // 4 identical entries
        },
  }
--- FAIL: TestStorageClusterHelmTemplate (0.00s)
    --- FAIL: TestStorageClusterHelmTemplate/TestOverrideNamespace (0.07s)
        storagecluster_helm_template_test.go:323:
                Error Trace:    /app/test/utils/test_utils.go:36
                Error:          Not equal:
                                expected: false
                                actual  : true
                Test:           TestStorageClusterHelmTemplate/TestOverrideNamespace
FAIL
exit status 1
FAIL    github.com/portworx/helm/test/portworx  0.080s

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