Investigate and adjust to changes in AWS creds coupling to in-cluster creds

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There are changes with how EKS clusters api-server recognize AWS users, related docs are AWS docs on cluster access entries. There was also a default change in eksctl making new clusters setup by default with support for new and old coupling system.

• If we transition from "only old" to "old and new", we can't go back, and if we transition from "old and new" to "only new" we can't go back. New clusters are now in "old and new" mode, while old clusters are in "only old" mode. Do we want to transition all clusters to "old and new" mode, and possibly just "new" mode?
• Anywhere we document using eksctl create iamidentitymapping, we are documenting things related to the old system.
• The new system seems to provide EKS cluster permissions for account admins.

Example from old cluster

Example from new cluster

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Useful command:

• Add utils command to migrate iamidentitymappings to EKS access entries eksctl-io/eksctl#7710

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Changes made

AWS accounts with SSO signin

These are all now "new + old" system, except 2i2c-aws-us that is new system only and piloting that. These accounts no longer require the aws-auth configmap to my knowledge, and we could transition to "new only" for all of these I believe if we'd want.

If that is wanted, the command to run is eksctl utils migrate-to-access-entry --cluster $CLUSTER_NAME --approve --target-authentication-mode=API

• 2i2c-aws-us (new only)
• catalystproject-africa
• gridsst
• jupyter-health
• kitware
• nasa-cryo
• opensci
• smithsonian
• ubc-eoas
• victor

The accounts below are pending deletion in #4097, no action are taken here - the hub deployer user doesn't exist here either so it errored when I tried before realizing they were being decomissioned.

• bican
• dandi
• linc

Other accounts

I've migrated these as well to the old + new system - I wonder if we can avoid needing to declare accessentries for individual users here as well.

• earthscope
• jupyter-meets-the-earth
• nasa-esdis
• nasa-ghg
• nasa-veda
• openscapes
• projectpythia