Fix device failures on runtime-extra-platforms

[kotlarmilos]

Description

This PR adds the --user parameter to the devicectl device copy command to resolve device failures on runtime-extra-platforms. While this parameter appears to be optional on iOS, it is required on tvOS:

Error: If you are targeting a data container, you must specify a username.
[18:27:04] dbug: Usage: devicectl device copy from --device <uuid|ecid|udid|name> --source <source> [--destination <destination>] [--user <user>] --domain-type <domain-type> [--domain-identifier <domain-identifier>] [--verbose] [--quiet] [--timeout <seconds>] [--json-output <path>] [--log-output <path>]

The fix was validated locally on iOS 18.5.

Contributes to dotnet/runtime#117714