timecraft: add describe command

[achille-roussel]

This PR adds a new describe sub-command to timecraft, the intent being to provide detailed information about specific resources listed out by get.

Here are a few examples:

$ ./timecraft describe ps eb6b60d1-4636-4f1f-85ad-375a3c063283
ID: eb6b60d1-4636-4f1f-85ad-375a3c063283
Start Time: 1h ago, Mon, 29 May 2023 14:24:22 PDT
Runtime: timecraft (devel)
Modules:
  714c48844052: (none) (6.82 MiB)
Args:
  http.wasm
  /Users/achilleroussel/wasm/http.wasm
Env:
  LANG=en_US.UTF-8
  PWD=/Users/achilleroussel/go/src/github.com/stealthrocket/timecraft
  ...
Log:
  segment 0: 1.72 KiB, created 1h ago (Mon, 29 May 2023 14:24:24 PDT)

$ ./timecraft describe ps eb6b60d1-4636-4f1f-85ad-375a3c063283 -o json
{
  "descriptor": {
    "mediaType": "application/vnd.timecraft.process.v1+json",
    "digest": "sha256:fc36c9197d6c6840b7ef98d85615b1f75d1a4c2aca9495322b3a66b3927df0d2",
    "size": 396,
    "annotations": {
      "timecraft.object.media-type": "application/vnd.timecraft.process.v1+json"
    }
  },
  "data": {
    "id": "eb6b60d1-4636-4f1f-85ad-375a3c063283",
    "startTime": "2023-05-29T14:24:22.699595-07:00",
    "config": {
      "mediaType": "application/vnd.timecraft.config.v1+json",
      "digest": "sha256:6d80ee83e97eb2f72b1167872041f9c496a043865d1214b1be2b2d67873f9fc2",
      "size": 2964,
      "annotations": {
        "timecraft.object.media-type": "application/vnd.timecraft.config.v1+json"
      }
    }
  }
}

$ ./timecraft describe ps eb6b60d1-4636-4f1f-85ad-375a3c063283 -o yaml
descriptor:
  mediaType: application/vnd.timecraft.process.v1+json
  digest: sha256:fc36c9197d6c6840b7ef98d85615b1f75d1a4c2aca9495322b3a66b3927df0d2
  size: 396
  annotations:
    timecraft.object.media-type: application/vnd.timecraft.process.v1+json
data:
  id: eb6b60d1-4636-4f1f-85ad-375a3c063283
  startTime: 2023-05-29T14:24:22.699595-07:00
  config:
    mediaType: application/vnd.timecraft.config.v1+json
    digest: sha256:6d80ee83e97eb2f72b1167872041f9c496a043865d1214b1be2b2d67873f9fc2
    size: 2964
    annotations:
      timecraft.object.media-type: application/vnd.timecraft.config.v1+json

[achille-roussel]

I moved this to the run command which is the only case where we need to perform graceful shutdowns. It helps interrupt CLI commands with Ctrl+C.

[achille-roussel]

I removed this because it causes the hash to change for every object.