add --config-file to all commands

[errordeveloper]

Currently some commands still don't support --config-file, we should add it to all commands, and add --validate as well to allow users to control validation (#1124 already adds a field for it).
Verify that all commands support these flags

[Callisto13]

For anyone coming by to pick part of this up, these are the commands which as yet do not support the --config-file flag:

• get cluster
• get labels
• set labels
  - [ ] unset labels see comment at bottom of thread
• utils describe-stacks
  - [ ] utils schema doesn't require cfg file
  - [ ] utils update-cluster-stack command removed
• utils update-legacy-subnet-settings
• utils write-kubeconfig

[neha-viswanathan]

Hello I can pick this up

[Callisto13]

Hey @neha-viswanathan sure, go for it!

I think let's have a PR for each action, to make reviewing etc easier 👍