Use go API instead of local command execution where possible

[petersutter]

In the code you often see stuff like

• ExecCmdReturnOutput("bash", "-c", "curl <something>")
• ExecCmdReturnOutput("bash", "-c", "export KUBECONFIG="+currentConfig+"; kubectl <something>") etc.

Instead of using curl and kubectl, use go APIs where possible

[tedteng]

/assign

[dansible]

It may be good to evaluate how many times we are using curl/kubectl and evaluate if we need to split this into two tasks

[neo-liang-sap]

i will work on curl part in https://github.com/gardener/gardenctl/issues/273

[tedteng]

will working on ExecCmdReturnOutput("bash", "-c", "export KUBECONFIG="+currentConfig+"; kubectl <something>") insteading of using kubectl, use go APIs where possible . https://github.com/gardener/gardenctl/issues/281

[tedteng]

/assign