Add variables to configure Containerd default runtime, untrusted runt…

[pasqualet]

…ime and additional runtimes

What type of PR is this?
/kind feature

What this PR does / why we need it:

This PR enables the configuration of containerd runtimes: default runtime, untrusted runtime and additional runtimes.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Add configuration for containerd runtimes

[pasqualet]

/assign @Miouge1

[Miouge1]

@pasqualet thank you for your contribution, could you add the new vars in the sample inventory as well?

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[pasqualet]

@Miouge1 I've updated the sample inventory

[pasqualet]

/assign @Atoms @Miouge1 @holmsten

[Miouge1]

Great! Looks good to me.

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Miouge1, pasqualet

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