allow deploying to multiple stacks in the same account

[gojko]

Using named roles prevents this stack from being deployed to multiple clusters in the same AWS account, and requires CAPABILITY_NAMED_IAM.

Physical role names aren't really important for the functioning here, and removing role names lets CFN auto-generate unique names, so the stack can be deployed safely multiple times in the same account to work with different clusters, and requires lower capabilities for deployment

Description of changes: Removed role names to let CFN automatically generate them

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