Variable CLAIM_DEVICE_MAC_KEYS`Const`

CLAIM_DEVICE_MAC_KEYS: readonly [
    "mac_addr",
    "macAddr",
    "mac",
    "MAC",
    "mac_address",
] = ...

Keys a device may use for its MAC in the claim-start payload, checked in order. The firmware payload is not part of the cloud contract, so several spellings are tolerated.