Handle extensions duplicates

[pPrecel]

Description

Handle extensions duplicates and inform user about it.

Expected result

We should add only the first found extension and inform user using the Extensions Warning section about other extensions that can't be processed

cli $ ./bin/kyma@v3 alpha --show-extensions-error
Extensions Warning:
failed to process configmap 'kyma-system/hana-2': resource with the same rootCommand already added
failed to process configmap 'kyma-system/hana-3': resource with the same rootCommand already added
failed to process configmap 'kyma-system/hana-4': resource with the same rootCommand already added

A set of alpha prototypes that may still change. Use in automations on your own risk.

Usage:
  kyma alpha [command]

Available Commands:
  access             Produce a kubeconfig with Service Account based token and certificate
  app                Manage applications on Kubernetes cluster.
  hana               Manage a Hana instance on the Kyma platform.
  module             Manage kyma modules.
  oidc               Create kubeconfig with an OIDC token
  provision          Provisions a Kyma cluster on the BTP.
  reference-instance Add an instance reference to a shared service instance.

Flags:
  -h, --help                    help for alpha
      --kubeconfig string       Path to the Kyma kubeconfig file.
      --show-extensions-error   Print possible error when fetching extensions failed.

Use "kyma alpha [command] --help" for more information about a command.

Actual result

cli $ ./bin/kyma@v3 alpha
A set of alpha prototypes that may still change. Use in automations on your own risk.

Usage:
  kyma alpha [command]

Available Commands:
  access             Produce a kubeconfig with Service Account based token and certificate
  app                Manage applications on Kubernetes cluster.
  hana               Manage a Hana instance on the Kyma platform.
  hana               Set of commands for managing Functions
  hana               Set of commands for managing Functions
  hana               Set of commands for Dummies
  module             Manage kyma modules.
  oidc               Create kubeconfig with an OIDC token
  provision          Provisions a Kyma cluster on the BTP.
  reference-instance Add an instance reference to a shared service instance.

Flags:
  -h, --help                    help for alpha
      --kubeconfig string       Path to the Kyma kubeconfig file.
      --show-extensions-error   Print possible error when fetching extensions failed.

Use "kyma alpha [command] --help" for more information about a command.

Steps to reproduce

Create a few ConfigMaps with the same extension root command and use the kyma@v3 to fetch them and build commands.