feat: avoid duplicate of InferencPool golang types.

[capri-xiyue]

avoid duplicate of InferencPool golang types following https://github.com/kubernetes-sigs/gateway-api/blob/093f6538409c071e906856bd1ce4072204fb3f08/apis/v1beta1/gateway_types.go#L48-L55.

It comes with the limitation that the crd-gen will just generate v1 InferencePool CRD and won't generate alpha InferencePool CRD. It is probably because we are using https://github.com/kubernetes-sigs/gateway-api/blob/093f6538409c071e906856bd1ce4072204fb3f08/apis/v1beta1/gateway_types.go#L48-L55.
for InferencePool here with v1 and alpha InferencePool actually belongs to different groups, one with inferencepools.inference.networking.k8s.io and the other with inferencepools.inference.networking.x-k8s.io

The PR will cause

1. removal of inferencepools.inference.networking.x-k8s.io InferencePool CRD
2. removal of deepcopy generated code of any fields related to alpha type InferencePool like EndpointPickerConfig and InferencePoolSpec , only InferencePool and InferencePoolList will be kept.
3. Any inferencepools.inference.networking.x-k8s.io InferencePool CRD no longer exists, any test including inferencepools.inference.networking.x-k8s.io InferencePool CRD will need to get removed.

Here is the graph

InferencePool API Version	Group	API Types	Generated Client	CRD
v1alpha2	inference.networking.x-k8s.io	Yes	Yes	No
v1	inference.networking.k8s.io	Yes(use type InferencePool v1.InferencePool syntax)	Yes	Yes

Rationale
We'd encourage users and controllers to exclusively focus on the v1 API going forward, thus we omit the v1alpha2 CRD from the release. However, this PR leaves controllers with the option to support both v1a2 and v1 concurrently. An approach is to represent alpha InferencePool in v1 InferencePool but override the group to inference.networking.x-k8s.io

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[k8s-ci-robot]

Hi @capri-xiyue. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[capri-xiyue]

@robscott This include the efforts we work this afternoon to use code similar to https://github.com/kubernetes-sigs/gateway-api/blob/093f6538409c071e906856bd1ce4072204fb3f08/apis/v1beta1/gateway_types.go#L48-L55

[capri-xiyue]

/assign @kfswain

[capri-xiyue]

/assign @robscott

[kfswain]

/ok-to-test

[capri-xiyue]

/hold until #1118 get merged

[capri-xiyue]

I've deleted the generated client files and run make generate again, no more generated client will get deleted. So the PR capri-xiyue#2 already shows all the contents that need to get deleted @robscott