⭐️ allow and deny subscriptions + scan VMs options (#1477)

* ⭐️ allow and deny subscriptions + scan VMs options

This PR adds three more flags to the experimental command
`cnspec integrate azure`.

`--allow`, `--deny` used to control the integration of subscriptions.

`--scan-vms` that enables scanning VMs on Azure subscriptions via
RunCommand.

Additionally, I moved the `onboarding` code that is generic to its own
package so that new integration commands like `gcp` or `aws` can
leverage it.

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Signed-off-by: Salim Afiune Maya <[email protected]>