[MCL-5454] Converted profiles have name as key instead of random UUID

Affected version: 2.0.757 (Windows)

The bug

Profiles which were created with the old launcher has their names as key in the launcher_profiles.json file instead of a random UUID which every new profile has.

{
  "profiles": {
    "Snapshots": {
      "type": "latest-snapshot",
      "lastUsed": "1970-01-01T00:00:00.002Z",
      "gameDir": "###"
    },
    "691a56c5be968605778575592a6a5b85": {
      "name": "New profile",
      "type": "custom",
      "created": "2017-02-04T16:28:52.125Z",
      "lastUsed": "1970-01-01T00:00:00.000Z",
      "lastVersionId": "latest-release"
    }
}