Add Phase 2 COSI Support

[elainezhao1]

PR summary:

This is a phase 2 COSI support, we should now be able to generate cosi file from a non-verity base image with a verity config, and the verity information will be included in the cosi metadata file, so it will align with expected sample format

local test:
tested with command sudo ./imagecustomizer --log-level debug --build-dir ./build --image-file core-3.0.20241220.vhdx --output-image-file ./output-image-test.cosi --output-image-format cosi --config-file ../pkg/imagecustomizerlib/testdata/verity-config.yaml
unpacked the .cosi file

and obtained output/metadata.json

{
  "version": "1.0",
  "osArch": "amd64",
  "images": [
    {
      "image": {
        "path": "images/output-image-test_1.raw.zst",
        "compressedSize": 988946,
        "uncompressedSize": 8388608,
        "sha384": "6c2a78a9bc84624d90fdf2b0be7e33dd4abd305f8ae2467a4868bdf3ed8114cbe72c8512e5836e0a806e932732f79585"
      },
      "mountPoint": "",
      "fsType": "vfat",
      "fsUuid": "1163-42B5",
      "partType": "c12a7328-f81f-11d2-ba4b-00a0c93ec93b",
      "verity": null
    },
    {
      "image": {
        "path": "images/output-image-test_2.raw.zst",
        "compressedSize": 51437979,
        "uncompressedSize": 1064304640,
        "sha384": "f6594fa455d3feffd002dddd32afc843856e09bb850c6a3a6ec84366a00c8dde92e28f68a464ca62e8160bb5ad6a50e2"
      },
      "mountPoint": "",
      "fsType": "ext4",
      "fsUuid": "14e039a8-61d2-4d43-85b2-f26c92326c03",
      "partType": "0fc63daf-8483-4772-8e79-3d69d8477de4",
      "verity": null
    },
    {
      "image": {
        "path": "images/output-image-test_3.raw.zst",
        "compressedSize": 115309290,
        "uncompressedSize": 2147483648,
        "sha384": "29d8663dbd8f320ad9bba8169173837213eb973842f52ec774af8840f130c596b118cef88c2a4c38bc8820cfba482637"
      },
      "mountPoint": "",
      "fsType": "ext4",
      "fsUuid": "393703a2-b8a9-4574-8fd0-d961674c3efa",
      "partType": "0fc63daf-8483-4772-8e79-3d69d8477de4",
      "verity": {
        "image": {
          "path": "images/output-image-test_4.raw.zst",
          "compressedSize": 2908417,
          "uncompressedSize": 134217728,
          "sha384": "d4c8dd1357868b9aab271af8f74c52f05c8e4378d53637644cec43fc7a20adbb0aa1f0b01d701555cfda0490205d11ab"
        },
        "hash": "d5ff43f8d03a738b1e25f4eeb1b1f71441fa456daf60a664f64a2e95316ec65f"
      }
    },
    {
      "image": {
        "path": "images/output-image-test_5.raw.zst",
        "compressedSize": 28775661,
        "uncompressedSize": 2012217344,
        "sha384": "9a69d82c2e1c0b6681191cbcc6847ba8db2b54f15671b0b9a00e1649ce753038a8f2cb2b6d7e1bc36bdcc9cc8d0dbbf1"
      },
      "mountPoint": "",
      "fsType": "ext4",
      "fsUuid": "8fee3677-b8ba-432b-8add-3f336d11575f",
      "partType": "0fc63daf-8483-4772-8e79-3d69d8477de4",
      "verity": null
    }
  ],
  "osRelease": "",
  "id": "85e18600-1160-1b53-bcea-d93a3f0d848b"

Note:
A verity base image currently is not supported, will wait customizations on verity images to be enabled. Also, will have a follow-up pr to fix the missing mountpoints.

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Checklist

• Tests added/updated
• Documentation updated (if needed)
• Code conforms to style guidelines