netvsp: tracing improvements for error triage

[erfrimod]

Adding tracing spans to control-path operations in VF Manager to try and help answer two questions:

1. If a VF Manager operation like ManaDeviceRemoved fails to complete in a timely fashion, which 'await' call are we stuck in? It could be try_notify_guest_and_revoke_vtl0_vf(), shutdown_vtl2_device(), or update_vtl2_device_bind_state() and tracing spans will provide entry and exit opcodes.
2. If a VF Manager operation like ManaDeviceRemoved starts taking longer and missing SLAs, tracing spans can help us narrow down which call is taking up additional time.

• Improves NetVSP observability by adding structured tracing spans around VF Manager operations: VTL2 device startup/shutdown, VTL0 VF arrival/removal/revoke, endpoint disconnects, bind-state updates.
• Makes NetVSP device logging more actionable by adding instance_id and/or channel_idx to queue/channel errors: open/close/restore.
• Minor consistency improvements to error tracing. err => error and making that field the first element.
• Readability improvement to state transition logic in DataPathSwitchPending handler. Turning double-nested 'if' check into a 'match(a,b)'.
• Fixes to minor typos found in comments in net_mana and tracelimit..

[Copilot]

Pull request overview

This PR enhances observability and tracing in the NetVSP device by adding structured tracing spans around VF Manager control-path operations and improving error logging consistency.

Key changes:

• Adds tracing spans to VF Manager operations (VTL2 device startup/shutdown, VTL0 VF arrival/removal/revoke, endpoint disconnects, bind-state updates) to help identify which async operations are blocking or taking too long
• Standardizes error field naming from err to error and positions error fields first in trace logs for consistency
• Adds instance_id and/or channel_idx context to device and channel error logs for better diagnostics
• Refactors nested conditionals to match expressions for improved readability
• Fixes minor typos in comments

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
vm/devices/net/netvsp/src/lib.rs	Standardizes error logging (err→error), adds instance_id/channel_idx context to device errors, refactors state transition logic, removes redundant imports, fixes typos
vm/devices/net/net_mana/src/lib.rs	Fixes comment typos (Hardware→hardware, Encapsulation→encapsulation, affects grammar)
support/tracelimit/src/lib.rs	Fixes typo in documentation example (custome→custom)
openhcl/underhill_core/src/emuplat/netvsp.rs	Adds Display impl for Vtl0Bus, adds tracing spans to VF Manager operations, extracts update_vtl2_device_bind_state helper method, adds save_state tracing

[chris-oo]

LGTM but see comment if that's useful or not.

[chris-oo]

do you want to log the actual matrix of errors here or is it not useful?