fix issue with runtime permissions requiring rolebinding list

[kon-angelo]

How to categorize this PR?

/area control-plane
/kind bug
/platform azure

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Release note:

NONE

[github-actions]

This change refines the startup process by correctly scoping a one-time migration task. The cleanup for legacy Terraformer RBAC resources is now nested to ensure it only runs on shoot clusters, not garden clusters. This aligns its behavior with a similar migration for the Machine Controller Manager, making the logic more consistent and preventing unnecessary operations on the garden cluster. The overall functionality for shoot clusters remains unchanged, but the startup sequence is now more precise.

Walkthrough

• Refactor: The startup logic has been improved to ensure legacy RBAC resource cleanup tasks are correctly scoped. The one-time migration task for cleaning up old Terraformer resources will now only execute for shoot clusters, preventing it from running unnecessarily in the garden cluster context. This enhances the robustness of the extension's startup process.

_{Model: gemini-2.5-pro | Prompt Tokens: 618 | Completion Tokens: 159}

[hebelsan]

/lgtm