Add ClusterRole aggregation for default user-facing roles

[khrm]

Add ClusterRole aggregation for admin, edit and view users. Refer: https://kubernetes.io/docs/reference/access-authn-authz/rbac/#aggregated-clusterroles

Changes

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Release Notes

NONE

[khrm]

Fixes #486

[khrm]

/retest

[sayan-biswas]

/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sayan-biswas

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[khrm]

@enarha Let's merge this before the release.

[khrm]

/retest

[khrm]

@enarha @adambkaplan Can you re-review this and give lgtm if OK?

[khrm]

Can you re-review this and give lgtm if it's alright, @adambkaplan @vdemeester ?

[enarha]

/lgtm