Shared Storage V2: Add native worker configuration and credential delivery

Description

Add worker support for loading ESS HCL from a supplied file and delivering metadata credentials through a Kubernetes Secret.

Requirements

• When ESS_HCL_SOURCE is set, copy that file verbatim into the ESS Agent shared configuration directory. Preserve generated HCL behavior when it is unset.
• When NVCF_METADATA_CREDENTIALS_SECRET_NAME and NVCF_METADATA_CREDENTIALS_SECRET_KEY are set, patch the configured Kubernetes Secret key.
• Preserve the existing /var/run/nvcf/info/self file path when the Kubernetes Secret settings are absent.
• Reject credentials that exceed the per-key Secret budget before calling the Kubernetes API.

Definition of Done

• Tests cover both HCL source paths, both metadata credential delivery paths, and oversize rejection before an API call.
• The implementation follows the repository's existing Kubernetes client dependency pattern.