feat(cli): add json output to attestation push

[migmartri]

This patch implements the json output for the att push command. This output includes the envelope in string format and its digest.

note that the default output is kept the same for compatibility reasons.

default view (not changed)

chainloop att push
INF push completed
{
   "payloadType": "application/vnd.in-toto+json",
   "payload": "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",
   "signatures": [
      {
         "keyid": "",
         "sig": "MEYCIQCeHU0WSYbfu3bVIEbapgLg5Z6cXv+6EEFPUofU7lgzkQIhAPVGq7Tg2j5gZTqX7Kxp/cIt+oM922RA0e3ZQ8gsFRYN"
      }
   ]
}

INF Attestation Digest: sha256:8403a35946fe9f2e81e5265306a5691faf4c24e2b8107da38f9778ef30aa38bf

new json output

chainloop att push -o json
INF push completed
{
  "digest": "sha256:2dc17f7c933d20e06b49250a582a3d19bdfbadba9c4e5f3f856af6f261db79d4",
  "envelope": "{\n   \"payloadType\": \"application/vnd.in-toto+json\",\n   \"payload\": \"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\",\n   \"signatures\": [\n      {\n         \"keyid\": \"\",\n         \"sig\": \"MEUCIDGBc8J4tpGaSyTcdHecnZOa725Tja4tozwtXNr6jSz7AiEA8xOts32aCmDs3TaUTyV8Tiv461gblt+ysfCT2OH9DFU=\"\n      }\n   ]\n}\n"
}

Closes #728

[danlishka]

LGTM