[EKS] [request]: Ability to set the number of workers that create branch ENI for VPC RC

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**Tell us about your request**
Currently, Branch ENI creation in VPC RC is handled by a dedicated worker. The speed of branch ENI creation is determined by the number of workers, but it is currently impossible to change the number of workers.
Worker Count : https://github.com/aws/amazon-vpc-resource-controller-k8s/blob/master/pkg/config/loader.go#L138

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
When many pods are created at once, the pods are not created quickly due to the delay in branch ENI creation. I want to create branch ENI and pods more quickly by adjusting the number of Workers.

**Are you currently working around this issue?**

**Additional context**

**Attachments**

Start with pkg/config/loader.go around the referenced worker-count setting and determine how VPC Resource Controller configuration is loaded. Confirm how branch ENI creation workers are started and identify the project’s relevant tests or validation path. Done means the worker count can be adjusted and branch ENIs can be created in parallel as requested.

Written by the indexing model from the issue text.