Feature: Credential updates for nodepools

[Despire]

Motivation

Currently, there is no way to update credentials for existing nodepools. If provider API credentials or SSH private keys are rotated or expire, users must recreate the entire nodepool, causing unnecessary downtime and operational overhead.

Description

Allow users to update credentials in-place without requiring nodepool recreation. This includes provider credentials (e.g., AWS access keys, GCP service account JSON, Azure service principal secrets) for dynamic nodepools and SSH private keys for static nodepools. Updated credentials should be validated before being persisted and should not trigger any node reprovisioning or workload disruption.

Exit criteria

• Ensure updated credentials are propagated and used in subsequent operations without requiring nodepool restart or recreation