Change kubeconfigs from kcp-admin credentials to service specific credentials

[aaronschweig]

Current State
Currently, the kcp-admin kubeconfigs is used in all platform mesh services. We strive to have separate kubeconfigs for the service that give contain service specific kubeconfigs only with the rbacs needed, rather than full admin access

Todos

• Update to use service-specific kubeconfigs
• Ensure no component relies on kcp-admin kubeconfigs anymore
• During implementation, provide a mechanism to influence the generated service kubeconfigs, allowing customization as needed, but also ensure there are sane defaults for internal platform mesh services
• Review all places where kcp-admin kubeconfigs are currently in use