Fix device.Decode() return type

[jpm-canonical]

The bus.Devices() function returns a value, not a pointer, making the machine info []any a slice of values. The Decode() functions returned pointers, making the devices an array of pointers.

This PR changes the decode functions to also return values, instead of pointers.

[Copilot]

Pull request overview

This PR aligns the per-bus device JSON decoding APIs with how devices are produced elsewhere in the codebase (as concrete struct values in []any), by changing Decode() functions to return values instead of pointers.

Changes:

• Updated usb.Decode, pci.Decode, and fastrpc.Decode to return Device values (and Device{} on error) instead of *Device.
• Updated device and machine decode tests to assert against pci.Device/usb.Device values instead of pointers.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/machine/device/usb/usb.go	Change Decode() to return usb.Device by value.
pkg/machine/device/pci/pci.go	Change Decode() to return pci.Device by value.
pkg/machine/device/fastrpc/fastrpc.go	Change Decode() to return fastrpc.Device by value.
pkg/machine/device/decode_test.go	Update type assertions to expect value types from device.Decode.
pkg/machine/decode_test.go	Update type assertions to expect value types in MachineInfo.Devices.

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