Adding the ability to set the mirror parameter for the helm-repository

[ivanovpavel1983]

I cannot start the agent through the operator on hosts where there is no Internet access.

{"level":"info","ts":1677490206.879658,"logger":"instana.agent.controller.helm-reconcile","msg":"...Unable to get an update from the "instana-agent" chart repository (https://agents.instana.io/helm):\n\tGet "https://agents.instana.io/helm/index.yaml\": dial tcp 35.186.234.48:443: connect: connection timed out\n"}

{"level":"error","ts":1677490206.879732,"logger":"instana.agent.controller.helm-reconcile","msg":"Failure loading or validating Instana Agent Helm Chart, cannot proceed installation","error":"stat : no such file or directory","stacktrace":"github.com/instana/instana-agent-operator/controllers.(*InstanaAgentReconciler).Reconcile\n\t/workspace/controllers/instanaagent_controller.go:240\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler\n\t/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.2/pkg/internal/controller/controller.go:298\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem\n\t/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.2/pkg/internal/controller/controller.go:253\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2\n\t/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.9.2/pkg/internal/controller/controller.go:214"}

Is it possible to add a repository mirror option to the internal network?