Remove IBMPowerVS v1beta2 apiVersion

[Karthik-K-N]

This issue is created to track and plan of removal of IBMPowerVS v1beta2 apiVersion.

CAPI release support:

1. The Cluster API team will release a new Cluster API version approximately every four months (three releases each year)
2. CAPI supports upto N-2 releases and skip upgrades from N-3 to N (i.e v1.6 we can upgrade to v1.9)

More info about support can be found here https://cluster-api.sigs.k8s.io/reference/versions#cluster-api-release-support

apiVersion guidelines:

1. New apiVersion will be supported at least 9 months or 3 minor releases after a newer API version will be released
2. Kuberentes deprecation policy: https://kubernetes.io/docs/reference/using-api/deprecation-policy/

IBMPowerVS v1beta2 apiVersion removal roadmap

Release Date	CAPI	CAPIBM	v1beta2	v1beta3	Notes
December 2025	v1.12	v0.13	Served: true, Storage
April 2026	v1.13	v0.14	Served: true	Served: true, Storage	v1beta3 added
August 2026	v1.14	v0.15	Served: true	Served: true, Storage
December 2026	v1.15	v0.16	Served: true	Served: true, Storage
April 2027	v1.16	v0.17	Served: false	Served: true, Storage	v1beta2 unserved
August 2027	v1.17	v0.18	Served: false	Served: true, Storage
December 2027	v1.18	v0.19	Served: false	Served: true, Storage
April 2027	v1.19	v0.20	Served: false	Served: true, Storage
August 2028	v1.20	v0.21		Served: true, Storage	v1beta2 removed

Notes:

1. v0.14-v0.16: We have to keep v1beta2 served for 3 versions after introduction of v1beta3 according to the Kubernetes deprecation policy
2. v0.17-v0.20: We have to keep v1beta2 around for 4 versions after it was unserved, to ensure that managedField cleanup is run even if someone upgrades from n-3 => n.