capa-iam-operator refactoring

[alex-dabija]

Task

capa-iam-operator refactoring.

• We should have a central library for idempotent, well-tested functions (such as getOrCreateIAMRole, upsertIAMPolicyForRole, ...)
• Remove tests that only check internals without reconcilation (template_test.go)
• Specify at one place which roles we want to have and don't call external-dns "Route53"
• We seem to attach two equal policies each (e.g. control-plane-*-policy vs. irsa-role-*-policy). Fix that.
• Cluster should clean up all the bad stuff it created in its older versions :(
• Since the 3 controllers do the same, they should share most code. Also, we should lock a mutex while calling the AWS SDK, since otherwise we may get false-positive errors while creating the same object at the same time.
• Check if we really need to have a finalizer on the AWSCluster object or if we could even live without fetching that object at all