[ca] fix: undo Scale operation when a scaleUpRequest times out

[thatmidwesterncoder]

What type of PR is this?

/kind bug

What this PR does / why we need it:

This PR modifies the cluster-autoscaler to automatically revert (decrease) the target size of a node group when a scale-up request times out.

Currently, when a scale-up fails due to infrastructure provider capacity limits (e.g., CAPI infrastructure provider cannot provision new nodes), the autoscaler removes the scale-up request from tracking and puts the node group in backoff, but it does not decrease the target size back to its original value. This causes the infrastructure provider to indefinitely retry provisioning the failed nodes, even after the workload that triggered the scale-up has disappeared. Manual intervention is required to scale the cluster back down.

With this fix, when a scale-up request times out:

1. The autoscaler calls DecreaseTargetSize() on the node group to revert the increase
2. If the decrease fails, a warning is logged and an event is emitted
3. The scale-up request is then removed from tracking as before

This allows clusters running close to infrastructure capacity to automatically recover from failed scale-ups without manual intervention.

Which issue(s) this PR fixes:

Fixes #9120

Special notes for your reviewer:

• The DecreaseTargetSize method is called with a negative value equal to the original Increase from the scale-up request
• Error handling is in place - if the decrease fails, we log a warning and emit an event, but still proceed with removing the scale-up request and applying backoff
• Existing tests were updated to include WithOnScaleUp handler since the test provider now needs to handle the decrease operation
• Three new test cases were added:
  • TestExpiredScaleUpRevertsTargetSize - verifies target size is decreased on timeout
  • TestExpiredScaleUpRevertsTargetSizeHandlesError - verifies graceful handling when decrease fails
  • TestExpiredScaleUpRevertsPartialIncrease - verifies correct decrease amount for partial increases

Does this PR introduce a user-facing change?

Cluster-autoscaler now automatically reverts the target size of a node group when a scale-up request times out. This prevents cloud providers from indefinitely retrying failed node provisioning attempts after infrastructure capacity limits are hit.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: thatmidwesterncoder / name: Jacob Lindgren (4917022)

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