[Feature] Add support for Capacity Blocks in eksctl config file schema

[iankouls-aws]

What feature/behavior/change do you want?

Please add support for EC2 capacity blocks to the capacityReservation configuration in eksctl config files

Why do you want this feature?

Currently the capacityReservation feature supports on-demand capacity reservations (ODCR) and this has been very helpful, however with the release of Capacity Blocks in 2024 the need has expanded to support capacity blocks as well.
Capacity blocks are similar to ODCR, except they are completely self-service, and typically short-lived. Adding a managed or unmanaged node group using a capacity block is already supported by the AWS CLI and CloudFormation. Enabling this functionality in eksctl will simplify the process of adding capacity-block bound node groups to EKS clusters.

[bryantbiggs]

we're working on it @iankouls-aws !