Remove multiple pods sharing one claim in prepareResourceClaim

[ngcxy]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Previously prepareResourceClaim implements the iteration over pods reserved for a single claim. This is a preparation work for the scenario where a single claim could be shared among multiple pods, when they're claiming a shared device. Currently this logic is never used since shared device hasn't been introduced yet.

Our finalized design came out that even in shared device scenarios, each pod will get its own distinct ResourceClaim, and the driver handles subinterface creation per claim. Therefore this iteration over multiple pods becomes redundant.

This change removes this logic to simply the preparation logic given this design.

Which issue(s) this PR is related to:

Special notes for your reviewer:

Does this PR introduce a user-facing change?

- Add 1:1 pod-to-claim enforcement
  - Previously the driver allows preparing resource for a claim reserved by multiple pods (in rare and anti-pattern case when they are created simultaneously with the same claim).
  - Now it fails the preparation if the reserved reference is larger than one.
- Non-pod fail-fast
  - Previously a claim containing single non-pod reference would succeed silently.
  - Now it fails resourceClaim preparation with the validation error.

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[k8s-ci-robot]

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[gauravkghildiyal]

Thanks @ngcxy

/ok-to-test

[gauravkghildiyal]

/assign

[anson627]

/lgtm

[gauravkghildiyal]

Thanks!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauravkghildiyal, ngcxy

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