fix(platform/eks): Configurable VPC CNI params

Description

I can't figure out how to configure the CNI params for the alert. The defaults always take precendence. This was my solution to it, if someone has a working solution of a top level overwrite as below:

    values+:: {
      awsVpcCni+:: {
        minimumWarmIPs: 100,
        minimumWarmIPsTime: '50m',
      },

I'll close this pr if there's a way to do it.

Type of change

What type of changes does your code introduce to the kube-prometheus? Put an x in the box that apply.

• [ ] CHANGE (fix or feature that would cause existing functionality to not work as expected)
• [ ] FEATURE (non-breaking change which adds functionality)
• [x] BUGFIX (non-breaking change which fixes an issue)
• [ ] ENHANCEMENT (non-breaking change which improves existing functionality)
• [ ] NONE (if none of the other choices apply. Example, tooling, build system, CI, docs, etc.)

Changelog entry

Please put a one-line changelog entry below. Later this will be copied to the changelog file.

fix(platform/eks): Configurable VPC CNI params