fix(nodepool): add spot MHC cleanup on NodePool deletion

[dpateriya]

Background

When a NodePool with spot instances enabled is deleted, the deletion path in nodepool_controller.go (around line 527) only cleans up the regular MHC, not the spot-specific MHC (<nodepool-name>-spot).

This can leave orphaned spot MHC resources in the control plane namespace after the NodePool is removed.

Proposed Change

Update the NodePool deletion path to also delete the spot MHC alongside the regular MHC.

Context

• Identified during review of PR OCPBUGS-86798: spot MHC not created when autoRepair=true and ignition endpoint not reached #8645
• The spot MHC is created in reconcileSpotMachineHealthCheck with the name pattern <nodepool-name>-spot