🐛 Bypass PDBs during drain when node is unreachable

[rafael-azevedo]

Fixes #13508

What this PR does / why we need it:

When a node becomes unreachable (e.g. the underlying instance is stopped), CAPI's machine drain gets stuck indefinitely. The drain uses the Kubernetes Eviction API which respects PDBs. When pods on the unreachable node have PDBs with minAvailable: 1 and currentHealthy: 0, the Eviction API returns 429 TooManyRequests and drain retries forever.

The existing code correctly detects unreachable nodes but relies on the taint manager to bypass PDBs. When the instance is stopped/terminated, kubelet is not running and cannot execute the taint manager's deletions and pods linger indefinitely.

This adds a DisableEviction option to the drain helper that uses direct pod deletion instead of the Eviction API. This is set when the node is unreachable, since pods are not actually running and PDB protection is not meaningful.

/area machine

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: rafael-azevedo / name: Rafael Azevedo (23ccb46)

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