Investigate possible issues in metazone resolution data

[sffc]

For example, metaZones.json has this data for Europe/Kaliningrad:

            "Kaliningrad": [
              {
                "usesMetazone": {
                  "_mzone": "Moscow",
                  "_to": "1989-03-25 23:00"
                }
              },
              {
                "usesMetazone": {
                  "_mzone": "Europe_Eastern",
                  "_from": "1989-03-25 23:00",
                  "_to": "2011-03-27 00:00"
                }
              },
              {
                "usesMetazone": {
                  "_mzone": "Europe_Further_Eastern",
                  "_from": "2011-03-27 00:00",
                  "_to": "2014-10-25 23:00"
                }
              },
              {
                "usesMetazone": {
                  "_mzone": "Europe_Eastern",
                  "_from": "2014-10-25 23:00"
                }
              }
            ],

However, this gets transformed to only

    "rukgd": {
      "2014-10-25 23:00": 51
    },

Unclear what's going on here.

There are other examples, too. America/Ciudad_Juarez has

            "Ciudad_Juarez": [
              {
                "usesMetazone": {
                  "_mzone": "America_Central",
                  "_to": "1998-04-05 09:00"
                }
              },
              {
                "usesMetazone": {
                  "_mzone": "Mexico_Pacific",
                  "_from": "1998-04-05 09:00",
                  "_to": "2022-10-30 08:00"
                }
              },
              {
                "usesMetazone": {
                  "_mzone": "America_Central",
                  "_from": "2022-10-30 08:00",
                  "_to": "2022-11-30 06:00"
                }
              },
              {
                "usesMetazone": {
                  "_mzone": "America_Mountain",
                  "_from": "2022-11-30 06:00"
                }
              }
            ],

but it gets mapped to only

    "mxcjs": {
      "1998-04-05 09:00": 100,
      "2022-10-30 08:00": 10,
      "2022-11-30 06:00": 12
    },

(the fact that it was in America_Central prior to 1998 is not tracked)

CC @robertbastian