Set helm 3.0 as default

[verwilst]

What type of PR is this?
/kind feature

What this PR does / why we need it:
This changes the default helm version to v3.0.

Does this PR introduce a user-facing change?:

action required!

Users will have to be made aware how they can migrate their existing v2 objects to v3 (https://helm.sh/docs/topics/v2_v3_migration/ and https://github.com/helm/helm-2to3), and be told the following:

• Upgraders will still have Tiller running, so only when they use the helm binary on their api/master nodes will they have to do something. I think a lot of people use local helm binaries as well, which won't be impacted.
• New installs won't have a Tiller, so can only use Helm v3. They either have to change helm_version or be made aware of the namespaced scope of v3.

Upgrading to Helm v3

This release installs Helm v3 by default. You can stop this from happening by setting `helm_version = 'v2.16.1'` for example in `group_vars/k8s-cluster/addons.yml`.

When this is an upgrade of an existing cluster, follow the steps outlined by https://helm.sh/docs/topics/v2_v3_migration/ and https://github.com/helm/helm-2to3 afterwards to convert your Helm v2 releases to v3.

After the upgrade to Helm v3, Tiller will still be running on your cluster, but the `helm` binary on the api/master nodes will be replaced by a v3 counterpart. You won't be able to access/modify/upgrade your Helm v2 releases by using the default 'helm' binary on those nodes. Please manually download a Helm v2 binary on your workstation to modify existing v2 releases, or use the 2to3 plugin to convert everything to v3.

You will have to remove Tiller from your cluster manually ( or through the 2to3 plugin cleanup action) after everything has been migrated to v3.

[Miouge1]

@verwilst brilliant!

Looks good to me. @mirwan any additional feedback on this (I think you were involved in the previous Helm 3 discussions) ?

/lgtm

[mirwan]

@Miouge1 Thx for asking. It's fine with me of course

[verwilst]

Can we sign the deal with an approval? ;-)

[holmsten]

Looks good, but v3.0.3 is released now. Can you update while we're waiting for an approver? :)

[holmsten]

/lgtm

[Atoms]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Atoms, verwilst

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[Miouge1]

I'm rebasing this on latest master, that should fix the error in CI.

[Miouge1]

/lgtm