Extract fargate related code into a standalone file

[dims]

Fargate Node is a "variant" of regular EC2 nodes and needs special processing, originally the code for handling this variant was sprinkled across the code base. In this PR, we split it out behind the Variant interface and it also gets registered using RegisterVariant when the package is imported explicitly. For now this is good enough to inspect how the code is different for this variation of the regular code as well as make changes if/when needed. We can even figure out how to use tags to build aws-cloud-controller-manager without this variant getting registered for example for CAPA or kops etc. If in the future there is a need for something other variant, we can cleanly drop in another package if needed similar to how we do this for fargate.

NOTE: design is based on how we implemented support for different container runtimes in cadvisor: https://github.com/google/cadvisor/tree/master/container

[k8s-ci-robot]

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[hakman]

@dims You will probably need to rebase to fix govulncheck.

[dims]

@dims You will probably need to rebase to fix govulncheck.

thanks @hakman Done!

[dims]

/release-note-none

[dims]

/kind cleanup

[dims]

/assign @hakman @kmala @cartermckinnon /hold

[k8s-ci-robot]

@dims: GitHub didn't allow me to assign the following users: kmala.

Note that only kubernetes members with read permissions, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time. For more information please see the contributor guide

In response to [this](https://github.com/kubernetes/cloud-provider-aws/pull/917#issuecomment-2119066901): >/assign @hakman @kmala @cartermckinnon >/hold Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.

[rsumukha]

Ran a prow test suite against to validate Fargate tests, it was mostly successful with an unrelated test failure. gtg from Fargate side

[kmala]

/lgtm

[k8s-ci-robot]

@kmala: changing LGTM is restricted to collaborators

In response to [this](https://github.com/kubernetes/cloud-provider-aws/pull/917#issuecomment-2126232954): >/lgtm Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.

[dims]

/hold cancel

[hakman]

/lgtm

[hakman]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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