docs: Fix instructions for building iso

[nirs]

Testing shows that we need changes changes:

• x86_64 cpu
• Ubuntu 22.04
• docker is required even if building without docker
• python2 instead of python
• genisoimage (for mkisofs)
• Installing Go manually (Ubuntu 22.04 have only Go 1.18)
• Target should be minikube-iso-aarch64 or minikube-iso-x86_64. Using
  arm64 and amd64 fails.

I also cleaned up a little bit the formatting to make it easier to
maintain (one package per line).

Tested building:

• minikube-iso-aarch64
• minikube-iso-x86_64

I tests only the arm64 iso image.

[k8s-ci-robot]

Hi @nirs. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[minikube-bot]

Can one of the admins verify this patch?

[medyagh]

thank you for updating this doc, been a long time since touched

[medyagh]

/lgtm

[k8s-ci-robot]

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