remove unused code, leftovers, and other zombies from sandbox-sre adoption

[MatousJobanek]

KUBESAW-169

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 68.56%. Comparing base (f7f37c5) to head (82aebb2). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #60 +/- ## ========================================== + Coverage 67.83% 68.56% +0.73% ========================================== Files 44 43 -1 Lines 2515 2475 -40 ========================================== - Hits 1706 1697 -9 + Misses 617 586 -31 Partials 192 192 ``` | [Files](https://app.codecov.io/gh/kubesaw/ksctl/pull/60?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubesaw) | Coverage Δ | | |---|---|---| | [pkg/assets/assets.go](https://app.codecov.io/gh/kubesaw/ksctl/pull/60?src=pr&el=tree&filepath=pkg%2Fassets%2Fassets.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubesaw#diff-cGtnL2Fzc2V0cy9hc3NldHMuZ28=) | `63.63% <ø> (ø)` | | | [pkg/client/client.go](https://app.codecov.io/gh/kubesaw/ksctl/pull/60?src=pr&el=tree&filepath=pkg%2Fclient%2Fclient.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubesaw#diff-cGtnL2NsaWVudC9jbGllbnQuZ28=) | `55.35% <100.00%> (+3.03%)` | :arrow_up: | | [pkg/cmd/ban.go](https://app.codecov.io/gh/kubesaw/ksctl/pull/60?src=pr&el=tree&filepath=pkg%2Fcmd%2Fban.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubesaw#diff-cGtnL2NtZC9iYW4uZ28=) | `73.58% <ø> (ø)` | | | [pkg/configuration/configuration.go](https://app.codecov.io/gh/kubesaw/ksctl/pull/60?src=pr&el=tree&filepath=pkg%2Fconfiguration%2Fconfiguration.go&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubesaw#diff-cGtnL2NvbmZpZ3VyYXRpb24vY29uZmlndXJhdGlvbi5nbw==) | `69.89% <ø> (+9.70%)` | :arrow_up: |