Add support for Kubernetes 1.34

[tobschli]

How to categorize this PR?

/area open-source usability
/kind enhancement
/platform openstack
/exp intermediate
/topology garden seed shoot
/merge squash

What this PR does / why we need it:
This PR adds support for Kubernetes 1.34 to the extension.

Which issue(s) this PR fixes:
Part of gardener/gardener#12814

Special notes for your reviewer:

• I have successfully validated the functionality as follows:
  • Create new clusters with versions < 1.34
  • Create new clusters with version = 1.34
  • Upgrade old clusters from version 1.33 to version 1.34
  • Delete clusters with versions < 1.34
  • Delete clusters with version = 1.34

Release note:

The provider-openstack extension does now support shoot clusters with Kubernetes version 1.34. You should consider the [Kubernetes release notes](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.34.md) before upgrading to 1.34.

Following the renaming based on [PR13273](https://github.com/gardener/gardener/pull/13273), **autonomous shoot cluster** was renamed to **self hosted shoot cluster**. This leads to e.g. a change of the `/gardener-extension-provider-azure`'s cli argument `--autonomous-shoot-cluster` to change to `--self-hosted-shoot-cluster` and the respective helm chart's variable `.Values.gardener.autonomousShootCluster` to change to `.Values.gardener.selfHostedShootCluster`.

[github-actions]

This update adds support for Kubernetes 1.34 and migrates to newer tooling versions while refactoring autonomous cluster terminology to use "self-hosted" naming conventions instead.

Walkthrough

• New Feature: Added support for Kubernetes 1.34.0+ with corresponding container images and conformance testing placeholders
• Refactor: Renamed autonomousShootCluster to selfHostedShootCluster across configuration files, Helm charts, and Go code for improved terminology consistency
• Chore: Updated dependencies including Gardener core (v1.131.2 → v1.132.1), Kubernetes APIs (v0.33.5 → v0.34.1), and controller-runtime (v0.21.0 → v0.22.4)
• Chore: Upgraded controller-gen from v0.18.0 to v0.19.0, updating all generated CustomResourceDefinition files with new version annotations

_{Model: claude-sonnet-4-20250514 | Prompt Tokens: 45986 | Completion Tokens: 225}

[hebelsan]

/lgtm