Add interactive builder in kubectl plugin

[mszostok]

Description

The builder is based on the existing code base but with adjustments like:

• removed kubectl merger
• added additional checks
• adjusted approach for namespace dropdown
• removed executor bindings (we don't have this info in plugin)
• small bug fixes
• etc.

If you have IntelliJ, just select

• kubectl_test.go and kubectl_cmd_builder_test.go files and click "Compare Files" (cmd+d)
• kubectl.go and kubectl_cmd_builder.go files and click "Compare Files" (cmd+d)

Changes proposed in this pull request:

• Support the same experience as previously.
• Notify about not supported verb:
  
• Notify about missing perms:
  
• For now, I used the config property with default values, here is an issue for doing that in dynamic way: Get allowed kubectl builder verbs and resources dynamically  #981

Testing

1. Build plugins: make build-plugins-single
2. Start plugin server: env PLUGIN_SERVER_HOST=http://host.k3d.internal go run test/helpers/plugin_server.go
3. Create cluster: k3d cluster create labs --image=rancher/k3s:v1.25.0-k3s1
4. Export kubeconfig env: export KUBECONFIG=/Users/$USER/.kube/config # set custom path if necessary
5. Update your configuration to enable botkube/kubectl plugin:

   plugins:
     repositories:
       botkube:
         url: http://host.k3d.internal:3000/botkube.yaml
   executors:
     plugin-based:
       botkube/kubectl:
         enabled: true
         config:
           defaultNamespace: "default"
           log:
             level: "debug"
           interactiveBuilder:
             allowed:
               namespaces:
                 - default
                 - bar
               verbs: ["api-resources", "explain", "get", "logs", "top", "exec", "apply"]
               resources: [ "deployments", "pods", "namespaces", ]

6. Try to remove/change the interactiveBuilder config.
7. Create a kubeconfig with lower perms, e.g. follow this guide: https://devopscube.com/kubernetes-kubeconfig-file/. Then export Kubeconfig export KUBECONFIG=/tmp/devops-cluster-admin-config and restart botkube.

Screen.Recording.2023-02-15.at.12.42.26.mov

Related issue(s)

• Extract Kubectl executor feature as a plugin #841

[pkosiec]

Looks very good! Awesome work 🥳
Just a few comments with open questions / small improvement requests.
Also see the review for the docs: kubeshop/botkube-docs#213

[pkosiec]

LGTM 🚀
(Disclaimer: didn't test it after resolving review commens, but the changes weren't invasive so 🤞 Let me know if I should double check it still works 😄)