runtime-rs: parse block-mounts annotation for volumeDevice passthrough

[TheRayquaza]

Summary

Parse io.katacontainers.volume.block-mounts annotation and convert matching volumeDevices into agent Storage objects, enabling block device passthrough via annotation in the Rust shim, mirroring Go runtime behavior.

DO NOT MERGE, blockers:

• missing auto format mounts
• runtime: Add annotation-based block device mounting #40

Test plan

Test C1 - Block annotation mounts

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: kata-val-e1-pvc-2
  namespace: default
spec:
  accessModes: [ReadWriteOnce]
  volumeMode: Block
  storageClassName: ephemeral-premium-v2-lrs
  resources:
    requests:
      storage: 1Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: kata-val-e1-2
  namespace: default
  annotations:
    io.katacontainers.volume.block-mounts: |
      {"/dev/block-vol": {"mount": "/data", "fstype": "ext4", "options": ["rw"]}}
spec:
  nodeName: us3-staging-dog-arbok-90eec5c94014646d000003
  runtimeClassName: kata-qemu-runtime-rs
  containers:
  - name: test
    image: registry.ddbuild.io/images/base/gbi-ubuntu_2204:release
    command: ["sleep", "3600"]
    volumeDevices:
    - name: block-storage
      devicePath: /dev/block-vol
  volumes:
  - name: block-storage
    persistentVolumeClaim:
      claimName: kata-val-e1-pvc-2

Pass signals:

• Pod reaches Running
• Can write to filesystem at the specified mount point

Test C2 - Invalid annotation JSON

apiVersion: v1
kind: Pod
metadata:
  name: kata-val-e3
  namespace: default
  annotations:
    io.katacontainers.volume.block-mounts: "not valid json {"
spec:
  nodeName: us3-staging-dog-arbok-90eec5c94014646d000003
  runtimeClassName: kata-qemu-runtime-rs
  containers:
  - name: test
    image: registry.ddbuild.io/images/base/gbi-ubuntu_2204:release
    command: ["sleep", "3600"]

Pass signals:

• Warning logged: error parsing block mounts annotation
• Pod start fails with a clean parse error (no panic)

[zaymat]

Looking at it again, I don't think this patch was ever merged into our main branch.

I think this is the PR but we never merged it: https://github.com/DataDog/kata-containers/pull/40/changes