Allow Service Account Annotations to be provided to Helm chart

[ChrisVanLawAtFanatics]

Is your feature request related to a problem? Please describe.
The ability to pass annotations for the operator service account would allow integration with IRSA.

Describe the solution you'd like
Provide a serviceAccountAnnotations value in the operator values.yaml.

Describe alternatives you've considered

Additional context
The ability to set eks.amazonaws.com/role-arn annotation on the service account created by the operator chart would improve the usability of the helm chart.

[ChrisVanLawAtFanatics]

proposed implementation: #1968