Migrate iam code to AWS SDK v2

[nrb]

Update calls in the following packages and files. Note that this is not necessarily an exhaustive list.

./cmd/clusterawsadm/cmd/bootstrap/iam/iam_doc.go
./cmd/clusterawsadm/converters/iam.go
./cmd/clusterawsadm/cloudformation/bootstrap/iam.go
./pkg/cloud/scope/iamauth.go
./pkg/cloud/services/mock_services/iam_authenticator_interface_mock.go
./pkg/cloud/services/eks/iam/iam.go
./pkg/cloud/services/iamauth/iamauth.go
./pkg/cloud/services/iamauth/mock_iamauth
./pkg/cloud/services/iamauth/mock_iamauth/iamauth_mock.go

[damdo]

See examples on how to migrate here: #5389

[alexander-demicev]

/assign

[alexander-demicev]

I will work on this issue