Make aws regions available as a map and cache it to speed up fetching.

{
  "af-south-1": {
    "Region": "af-south-1",
    "RegionDesc": "Africa (Cape Town)",
    "RegionCode": "af-south-1",
    "RegionFriendly": "Africa",
    "City": "Cape Town"
  },
  "ap-east-1": {
    "Region": "ap-east-1",
    "RegionDesc": "Asia Pacific (Hong Kong)",
    "RegionCode": "ap-east-1",
    "RegionFriendly": "Asia Pacific",
    "City": "Hong Kong"
  },
  ...
}

Adjusted from https://stackoverflow.com/a/72357524/1495086.