[processor/resourcedetection] Use cluster version for EKS identifier

[dloucasfx]

Description

-eks- substring exists on all eks releases from what we have seen and I also verified by checking the repo https://github.com/aws/eks-distro/tree/main
This PR changes the EKS logic to check the cluster version and check if it contains the substring _eks_ to flag the cluster as EKS.
Unit tests are updated and code cleaned up.

Link to tracking issue

Fixes: #39479

Testing

Unit test

2025-04-18T15:44:02.285Z	info	internal/resourcedetection.go:188	detected resource information	{"resource": {"cloud.account.id":"906383545488","cloud.availability_zone":"us-west-2a","cloud.platform":"aws_eks","cloud.provider":"aws","cloud.region":"us-west-2","host.id":"i-091f2d176accf9126","host.image.id":"ami-05dbe843e7dc0237c","host.name":"ip-192-168-103-137.us-west-2.compute.internal","host.type":"c6a.large","k8s.cluster.name":"OTL-UI-Cluster","os.type":"linux"}}