Remove v1alpha3 + v1alpha4 apiVersions

[sbueringer]

Tracking issue for v1alpha3 + v1alpha4 apiVersion removal. This will stay around for a while.

Context:

• CAPI supports 3 versions: for 2 versions we regularly release patch releases, for the 3rd one we create emergency patches on demand
• CAPI currently tests up to n-3 => n upgrades.
  • Note: This is not well documented at the moment, but we should follow-up.
  • Note: The n-3 => n policy in CAPI aligns to the corresponding policy in Kubernetes
• We want to make sure that removal of old apiVersions do not break the n-3 => n upgrade path. This means that we have to keep apiVersions around long enough that "storage version migration" and "managedField cleanup" are run.

v1alpha3 & v1alpha4

CAPI	Release date	v1alpha3 + v1alpha4	Notes
v1.9	Dec 24	Served: false
v1.10	April 25	Served: false	CRD migrator added
v1.11	August 25	Served: false
v1.12	December 25	Served: false
v1.13	April 26		v1alpha3 + v1alpha4 removed
v1.14	August 26
v1.15	December 26

Notes:

• v1.10-v1.12: We have to keep v1alpha3 + v1alpha4 around for 3 versions after the CRD migrator has been added, to ensure that managedField cleanup is run even if someone upgrades from n-3 => n

Tasks:

• [v1.13] Remove v1alpha3 + v1alpha4

For more context, see: #11894

[sbueringer]

/triage accepted
/assign
/lifecycle frozen

[sbueringer]

/milestone v1.13