[libvirt_manager] Add predictable network interface names via --target

[holser]

Assign deterministic TAP device names on the host by passing --target
to virsh attach-interface, so interface names survive VM reboots and
re-creations instead of getting arbitrary vnetN names from libvirt.

Naming convention: {vm_short}p{net_index} (e.g. compute0p0,
controller0p1). Controlled by cifmw_libvirt_manager_predictable_nic_names
(defaults to true).

[openshift-ci]

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[evallesp]

LGTM, asked for a TP.

[nemarjan]

(praise) Great improvement adding --target for predictable NIC naming.
(Question) : _target_dev is currently computed as (_vm_short ~ 'p' ~ (net_idx|int))[:15]. Because this relies on truncation to satisfy the 15‑char limit, there’s a chance of collisions for VMs with similar prefixes. Just another thing to mention, once net_idx goes to 2+ digits (p9 → p10), the suffix length changes and the truncation point shifts, which increases the chance of two different inputs collapsing to the same 15‑char string.

Would you be up for considering a slightly more collision‑resistant naming scheme that still stays within 15 characters (for example a fixed layout like <vm_prefix><short_hash_of _clean_vm>, using only letters and numbers)? Alternatively, a small guard/assert to catch duplicate targets early could also work nicely.