eks: add ephemeral `aws_eks_cluster_auth` resource #16378

Job	Run time
go mod download	23s
markdown-lint	21s
misspell	35s
go build	3m 50s
import-lint	42s
go test	14m 47s
terraform providers schema	32s
go generate	6m 44s
Sweeper Functions Not Linked	5m 4s
tfproviderdocs	12m 12s
	45m 10s

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