The CI should upload a json with version and checksum to S3, for the new update logic

[umbynos]

Similar to #736, the json file has to be placed in https://downloads.arduino.cc/CreateAgent/Stable/darwin-arm64.json and should contain:

{
    "Version":"1.2.8",
    "Sha256": "3ahZ78JAs3cNfK60jofS/PsWRQiJvV1sZUchGvCqyLY="
}

[umbynos]

We have to name the file darwin-amd64-bundle.json in order to not break the old autoupdate process. Furthermore, we do not distribute arm64 native binaries yet, but if you run runtime.GOARCH on an arm64 machine running the amd64 binary you get ARM64 because the check runs dynamically. That is a problem. To solve this problem, we have to mirror all the content of amd64 to arm64