Isolate per-device provider state in controller tests

[felix-kaestner]

The test provider was a singleton shared by all controllers. Every test creates a distinct Device via GenerateName, but the provider stored all state (DNS, BGP, NTP, LLDP, etc.) in flat fields on a single struct. This caused state bleed between test suites and intermittent failures.

Refactor the test provider into three parts:

• DeviceState: per-device mutable state (all resource fields, ConnectFailure, LastRebootTime), each with its own mutex
• DeviceStore: shared map of device name to DeviceState, with a StateFor(name) accessor that creates entries on demand
• Provider: lightweight per-reconcile instance created by the ProviderFunc factory, capturing the device name during Connect via the new Connection.DeviceName field

Add DeviceName to deviceutil.Connection and set it in GetDeviceConnection so the mock provider can identify the device without changing any controller code.

[github-actions]

Merging this branch changes the coverage (1 decrease, 2 increase)

Impacted Packages	Coverage Δ	🤖
github.com/ironcore-dev/network-operator/internal/controller/cisco/nx	69.56% (+4.50%)	👍
github.com/ironcore-dev/network-operator/internal/controller/core	63.42% (+1.81%)	👍
github.com/ironcore-dev/network-operator/internal/deviceutil	47.76% (-2.24%)	👎

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/ironcore-dev/network-operator/internal/deviceutil/deviceutil.go	47.76% (-2.24%)	67 (+9)	32 (+3)	35 (+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/ironcore-dev/network-operator/internal/controller/cisco/nx/bordergateway_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/cisco/nx/system_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/cisco/nx/vpcdomain_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/acl_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/banner_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/bgp_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/bgp_peer_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/certificate_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/configbackup_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/device_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/dhcprelay_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/dns_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/ethernetsegment_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/evpninstance_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/interface_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/isis_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/lldp_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/managementaccess_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/ntp_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/nve_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/ospf_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/pim_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/prefixset_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/probe_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/routingpolicy_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/snmp_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/suite_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/syslog_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/user_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/vlan_controller_test.go
• github.com/ironcore-dev/network-operator/internal/controller/core/vrf_controller_test.go