Update ec2 instances

[rehno-lindeque]

I ran the generate-ec2-properties.sh script and updated ec2-properties.nix with the new entries, while retaining any entries that would have been deleted.

(I've tried to replicate what was done in 75b1e1b0ab8d26289d2e7a688c5035eda7ec4f8f.)

New instance types:

• High memory instances
  • u-12tb1.112xlarge
  • u-6tb1.112xlarge
  • u-6tb1.56xlarge
  • u-9tb1.112xlarge
• G4ad instances (AMD Radeon Pro V520 GPUs)
  • g4ad.2xlarge
  • g4ad.xlarge

[rehno-lindeque]

Note that in all the cases where supportsNVMe was changed, it was changed from false to true. So I've retained those.