Create & initialise a new AWS account

[SamLR]

We want a new, secure, AWS account that can be used by engineers to deploy kubernetes clusters into.

Acceptance Criteria

• New account created as part of corp-infra
• Service control policy (SCP) created and applied that limits actions to those necessary to create EKS clusters & administer them
• Roles created for use by Weaveworks employees:
  • Administrator -- assumable by members of Blazing bonfire (this will have all permissions allowed by the SCP)
  • User -- assumable by anyone who will be able to create clusters this will only have the minimum permissions necessary to run eksctl
  • Readonly -- optional but probably something we can grant to anyone in the company in order to view the account

This will need to be done on the https://github.com/weaveworks/corp-infra repo and reviewed/applied by IT

cf https://github.com/weaveworks/corp/issues/2951

[SamLR]

https://github.com/weaveworks/corp-infra/pull/27 covers account creation. Think we may need to look for another/new github repo to handle creation of the IAM roles etc (this would likely form the basis for any other shared infra in future expansions)