How to categorize this issue?

/kind cleanup

What would you like to be added:
Let's drop support for Kubernetes versions <= 1.26 in October 2024. At the time of writing this issue, support for K8s 1.26 ended 5 months and 2 weeks ago. See https://endoflife.date/kubernetes.

Gardener:

• https://github.com/gardener/gardener: Drop support for Shoots with Kubernetes version <= 1.26 #10664

  • UnhealthyPodEvictionPolicy in the PDB spec for components can be unconditionally set to AlwaysAllow
  • EnableStaticTokenKubeconfig in the Shoot spec can deprecated and the maintenance reconciler can be adapted
  • PodEvictionTimeout in the Shoot spec can be removed in a future version
  • corev1.AnnotationTopologyMode constant can be used unconditionally
  • Remove validation related to seccompDefault
  • Adapt validation and doc string related to encryption config.
  • Adapt kubelet config (ProtectKernelDefaults etc.)
  • Adapt featuregates which are added or removed in <=1.26,

    gardener/pkg/utils/validation/features/featuregates.go

    Line 34 in 6b24aa7

    var featureGateVersionRanges = map[string]*FeatureGateVersionRange{

  • Adapt admissionplugins which are added or removed in <= 1.26,

    gardener/pkg/utils/validation/admissionplugins/admissionplugins.go

    Line 46 in e687892

    admissionPluginsVersionRanges = map[string]*AdmissionPluginVersionRange{

  • Adapt apigroups which are added or removed in <=1.26,

    gardener/pkg/utils/validation/apigroups/apigroups.go

    Line 30 in 5b76b2e

    apiGroupVersionRanges = map[string]*APIVersionRange{

  • Adapt KCM controllers which are added or removed in <= 1.26,

    gardener/pkg/utils/kubernetes/controllers.go

    Line 20 in 5b76b2e

    var APIGroupControllerMap = map[string]map[string]versionutils.VersionRange{

  • Adapt container images

• Drop GRM TokenInvalidator controller. In 1.27 LegacyServiceAccountTokenNoAutoGeneration becomes LockToDefault: true ref. [GRM] Drop TokenInvalidator controller and webhook and disable PodTopologySpreadConstraints webhook in favour of matchLabelKeys in deployment #11497

• Disable PodTopologySpreadConstraints webhook for seeds and use spec.topologySpreadConstraints[*].matchLabelKeys in deployments: ref [GRM] Drop TokenInvalidator controller and webhook and disable PodTopologySpreadConstraints webhook in favour of matchLabelKeys in deployment #11497

Extensions:

• provider-aws: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-provider-aws#1093
• provider-gcp: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-provider-gcp#879
• provider-azure: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-provider-azure#997
• provider-alicloud: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-provider-alicloud#742
• provider-openstack: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-provider-openstack#889
• provider-equinix-metal: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-provider-equinix-metal#328
• networking-calico: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-networking-calico#517
• networking-cilium: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-networking-cilium#431
• shoot-dns-service: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-dns-service#393
• shoot-cert-service: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-cert-service#309
• shoot-lakom-service: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-lakom-service#118
• shoot-oidc-service: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-oidc-service#253
• shoot-networking-filter: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-networking-filter#188
• shoot-networking-problemdetector: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-networking-problemdetector#190
• shoot-rsyslog-relp: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-rsyslog-relp#190
• os-gardenlinux: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-os-gardenlinux#207
• os-suse-chost: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-os-suse-chost#183
• os-ubuntu: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-os-ubuntu#157
• os-coreos: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-os-coreos#139
• runtime-gvisor: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-runtime-gvisor#151
• registry-cache: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-registry-cache#274
• shoot-falco-service: Drop support for Shoots with Kubernetes version <= 1.26 gardener-extension-shoot-falco-service#207
• oidc-apps-controller: Nothing to do.
• acl: Drop support for Seeds with Kubernetes version <= 1.26 stackitcloud/gardener-extension-acl#119

Test Infra:

• https://github.com/gardener/test-infra: Nothing to be cleaned up after Replace kubetest with hydrophone framework test-infra#536

K8s test infra:

• https://github.com/kubernetes/test-infra: Cleanup K8S v1.25 and v1.26 dashboards for Gardener kubernetes/test-infra#34489

Why is this needed:
Drop support for quite old K8s versions.