feat: Allow specifying boot_iam_role

[msvticket]

Unless you set use_asm it was previously not possible to set boot_iam_role. You couldn't add it with

boot_secrets                    = [
    {
        name  = "bootServiceAccount.annotations.eks\\.amazonaws\\.com/role-arn"
        value = "arn:aws:iam::${var.aws_account}:role/jx-boot-job"
        type  = "string"
    }
]

either, since it would be overwritten with an empty value,

Since the role can be used for other things than asm I added a new input to make that clear.

[ankitm123]

Just need to run make docs, and update read me, then merge it ...