New metadata format

[orcutt989]

This PR addresses:

• Snapshot engine: better metadata JSON format #451
• Snapshot Engine: Support filtering snapshots' metadata #447

This PR does not address:

• Snapshot Engine: Serve all snapshots' metadata on a single and fixed endpoint #446.
  • This will be covered in a different PR.

Additional changes:

• Ability to override snapshot network
  • This was done because ghostnet is actually ithacanet, but
• Added new --in memory during tezos rolling image import

Changes can be seen here:

https://ghostnet.xtz-shots.io/base.json

Overview of changes

• Flattened/simplified metadata JSON for each artifact
• We're now updating base.json with existing/available snapshot artifacts instead of appending to an infinite historical list of all snapshots ever created.

Preview

[
  {
    "block_hash": "BLa7XX2hQ723JqZBA98hHqYJZi8nkSN5piNg3GUxmB83UcTzXQY",
    "block_height": "796706",
    "block_timestamp": "2022-07-04T23:42:05Z",
    "filename": "tezos-ghostnet-rolling-tarball-796706.lz4",
    "url": "https://ghostnet.xtz-shots.io/tezos-ghostnet-rolling-tarball-796706.lz4",
    "sha256": "cbf9aa74d1167d8b902a30ec6443cc41be41c4764a61c6953ffd2822c3193caa",
    "filesize_bytes": "136773640",
    "filesize": "130M",
    "tezos_version": "cb9f439e (2022-05-05 11:55:24 +0200) (13.0)",
    "chain_name": "ghostnet",
    "history_mode": "rolling",
    "artifact_type": "tarball"
  },
  {
    "block_hash": "BLa7XX2hQ723JqZBA98hHqYJZi8nkSN5piNg3GUxmB83UcTzXQY",
    "block_height": "796706",
    "block_timestamp": "2022-07-04T23:42:05Z",
    "filename": "ghostnet-796706.rolling",
    "url": "https://ghostnet.xtz-shots.io/ghostnet-796706.rolling",
    "filesize_bytes": "310900736",
    "filesize": "296M",
    "sha256": "a12781e9f9b238943f51d67a80c0a14f639c8611dd0fe30e029093892f2879f9",
    "tezos_version": "cb9f439e (2022-05-05 11:55:24 +0200) (13.0)",
    "chain_name": "ghostnet",
    "history_mode": "rolling",
    "artifact_type": "tezos-snapshot"
  },
  {
    "block_hash": "BKoE2ZbimFoCMbYnNUcHzEQemfyVNEuueHreHU9rkVbeXE1ZWwU",
    "block_height": "796771",
    "block_timestamp": "2022-07-05T00:02:20Z",
    "filename": "tezos-ghostnet-rolling-tarball-796771.lz4",
    "url": "https://ghostnet.xtz-shots.io/tezos-ghostnet-rolling-tarball-796771.lz4",
    "sha256": "dd2191b3abae675e6221250337a9877efd8699a90defd0f7cd447131d1c4c694",
    "filesize_bytes": "136947185",
    "filesize": "130M",
    "tezos_version": "cb9f439e (2022-05-05 11:55:24 +0200) (13.0)",
    "chain_name": "ghostnet",
    "history_mode": "rolling",
    "artifact_type": "tarball"
  },
...
]

[nicolasochem]

Great job reducing the number of LOC.