Implement orka delete

⚠ This MR is based on top of !127 (merged) ⚠

Please merge first the dependent MR, then change the target branch here to master and continue with review

What does this MR do?

Adds autoscaler Orka provider delete support

Why was this MR needed?

Clean up VMs created by the autoscaler

What's the best way to test this MR?

Get your orka-cli token:

cat ~/.config/configstore/orka-cli.json | jq -r ".token"

Fill out your config.toml

Provider = "orka"
OS = "macos"

VMTag = "manual-qa"

[Orka]
BaseImage = "runner-12-20201203.img"
Cores = 3
Endpoint = "http://10.221.188.100"
Token = "token from orka-cli"

Connect to the VPN using the script in the orka repository:

path-to-orka/scripts/vpn.sh

Run:

 CUSTOM_ENV_CI_JOB_ID=$(date +%s) BUILD_FAILURE_EXIT_CODE=1 SYSTEM_FAILURE_EXIT_CODE=2 bash -c "go run cmd/autoscaler/main.go custom prepare && go run cmd/autoscaler/main.go custom cleanup"

What are the relevant issue numbers?

#42 (closed)