Get Instance to Branch ENI limits at runtime.

[abhipth]

Is your feature request related to a problem? Please describe.
Currently the Instance to Branch ENI Limits are Hard coded which means for each new Instance type added we need to do a new release of controller.

Describe the solution you'd like
If EC2 team can expose API in aws-sdk-go with the Instance -> Branch ENI Limits we can fetch this information at runtime without needing a new controller release.

We are working with EC2 team to evaluate this request.

[DavidHe1127]

Making an API that exposes the list public is a sought-after feature