Accounts Removed From AWS Organization Still Appear in UI

[svozza]

Describe the bug
When an account has been removed from an AWS Organization, it still appears in the account list in the Workload Discovery UI. This is because in AWS_ORGANIZATION mode the discovery process finds all the accounts in an organization using ListAccounts and ultimately writes them to the database without doing a diff to see if any have been deleted.

We should move the account discovery logic to the getAccounts GraphQL query and use ListAccounts as the source of truth rather than the DynamoDB table and only use the discovery process to persist WD specific information.

[svozza]

Due to the API limits to the ListAccounts API, moving the logic top the accounts API is not feasible.