style: rename VM config structs to use 'Spec' suffix

[Lencerf]

Rename various configuration and parameter structs across the codebase to use the 'Spec' suffix instead of 'Config' or 'Param'. This helps distinguish VM configurations from VirtIO device configurations which use 'Config' corresponding to the VirtIO standard.

Renamed:

• VmConfig -> VmSpec
• BoardConfig -> BoardSpec
• CpuConfig -> CpuSpec
• MemConfig -> MemSpec
• KvmConfig -> KvmSpec
• HvConfig -> HvSpec
• Payload -> PayloadSpec
• XxParam -> XxSpec (for devices and VFIO)

Updated all usages and tests.

Assisted-by: Antigravity:Gemini-3.5-Flash

[coveralls]

Coverage Report for CI Build 29472196711

Coverage decreased (-0.001%) to 27.412%

Details

• Coverage decreased (-0.001%) from the base build.
• Patch coverage: 215 uncovered changes across 23 files (52 of 267 lines covered, 19.48%).
• 10 coverage regressions across 6 files.

Uncovered Changes

Top 10 Files by Coverage Impact	Changed	Covered	%
alioth-cli/src/boot/boot.rs	89	37	41.57%
alioth/src/vm/vm.rs	31	0	0.0%
alioth/src/board/board_amd64/board_amd64.rs	22	0	0.0%
alioth/src/cpu/cpu_amd64/cpu_amd64.rs	14	0	0.0%
alioth/src/hv/kvm/vm/vm_amd64/vm_amd64.rs	17	5	29.41%
alioth/src/board/board.rs	11	0	0.0%
alioth/src/board/board_arm64.rs	9	0	0.0%
alioth/src/hv/kvm/kvm.rs	9	0	0.0%
alioth/src/virtio/dev/net/tap.rs	9	0	0.0%
alioth/src/virtio/dev/blk.rs	8	0	0.0%
Total (25 files)	267	52	19.48%

Coverage Regressions

10 previously-covered lines in 6 files lost coverage.

File	Lines Losing Coverage	Coverage
alioth-cli/src/boot/boot.rs	4	59.05%
alioth/src/hv/kvm/vm/vm_amd64/vm_amd64.rs	2	30.77%
alioth/src/hv/kvm/kvm.rs	1	0.0%
alioth/src/virtio/dev/blk.rs	1	0.0%
alioth/src/virtio/dev/fs/vu.rs	1	0.0%
alioth/src/vm/vm.rs	1	0.0%

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Coverage Stats

Relevant Lines:	14593
Covered Lines:	3881
Line Coverage:	26.59%
Relevant Branches:	1258
Covered Branches:	464
Branch Coverage:	36.88%
Branches in Coverage %:	Yes
Coverage Strength:	37.91 hits per line

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💛 - Coveralls