Migrate HypervisorMaintenanceController to SSA (status + eviction creation)

[fwiesel]

Two commits, both for HypervisorMaintenanceController:

1. Migrate status updates to Server-Side Apply

Server-Side Apply lets the controller own only HypervisorDisabled, Evicting, and Evicted, without overwriting status managed by other controllers.

Nova compute-service failures are reflected as HypervisorDisabled=Unknown before the error is returned for retry. This keeps status useful when a requested transition cannot be completed and prevents eviction from starting when disabling the service fails.

Enabling a compute service also clears forced_down, so a previous HA event cannot leave an enabled service treated as down.

2. Migrate Eviction creation to Server-Side Apply

SSA makes Eviction creation idempotent while preserving labels and owner references. The controller still reads the Eviction after applying it to observe its current status.

Depends on #335.

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[fwiesel]

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[joker-at-work]

As written in DMs, please check if we need to transport the ObservedGeneration into the calls to SetApplyConfigurationStatusCondition to not wipe the previous values or the whole field or its ownership.

[joker-at-work]

ObservedGeneration is unused so my previous comment doesn't matter.

[github-actions]

Merging this branch will increase overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/cobaltcore-dev/openstack-hypervisor-operator/internal/controller	71.14% (+0.42%)	👍

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/cobaltcore-dev/openstack-hypervisor-operator/internal/controller/hypervisor_maintenance_controller.go	85.00% (+4.20%)	120 (-5)	102 (+1)	18 (-6)	👍

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/cobaltcore-dev/openstack-hypervisor-operator/internal/controller/hypervisor_maintenance_controller_test.go