feat: export tests results as JSON

[notV4l]

Add an --export parameter to cairo-test accepting a path to export tests results as JSON.

use :

cairo-test ./src/tests.cairo --single-file --export ./tests.json

example results for Success / Fail :

[
  {
    "name": "tests::tests::test_1",
    "status": "Success",
    "gas_usage": 500
  },
 {
    "name": "tests::tests::test_2",
    "status": "Fail",
    "gas_usage": 1600,
    "error_messages": [
      "this is panic !!!",
      "with",
      "a long",
      "message"
    ]
  }
]

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This change is 

[orizi]

Reviewed all commit messages.
Reviewable status: 0 of 4 files reviewed, 1 unresolved discussion (waiting on @notV4l)

a discussion (no related file):
please add more information directly into TestsSummary and add an export function to it directly.
I believe this would lead to much simpler code.

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[mkaput]

Reviewable status: 0 of 4 files reviewed, 2 unresolved discussions (waiting on @notV4l and @orizi)

a discussion (no related file):
Blocking this because I do very much support this initiative, but I have big objections to the overall design of this feature.

• This is rolling custom schema instead of using universally accepted standard formats like JUnit XML output, or TeamCity Messages.
• One IMHO important use-case is omitted here: using in interactive test running UIs etc. like the test runner windows in IntelliJ and VSCode. For this to work, we need to stream messages to standard output instead of writing a single report to a file.

While it is completely possible to implement streaming output separately, I don't think it's good idea to have too many options? After all, streaming output can be easily piped to a file via shell, so it'd be functionally a superset.

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[notV4l]

I don't feel able to make modifs to make it work the way @mkaput described.
I could make a PR to fit @orizi requested changes (just let me know) but you maybe want to rework/implement this feature the way @mkaput suggested.
Anyway it could be convenient to have a simple JSON file as export option.

[orizi]

it does sound like @mkaput is correct - we should probably open this as an issue for contribution if you don't feel capable of doing it.

Reviewable status: 0 of 4 files reviewed, 2 unresolved discussions (waiting on @mkaput and @notV4l)