Allow internal messages from disallowed nodeIDs

[StephenButtolph]

Why this should be merged

Fixes handling of internal messages from disallowed nodeIDs.

How this works

Skips allowlist check for internal messages.

How this was tested

Added unit test.

Need to be documented in RELEASES.md?

[Copilot]

Pull Request Overview

This PR updates the networking layer to introduce and handle internal messages separately, skipping the usual allowlist check for internal nodeIDs, and adds unit tests and tracing support to cover the new behavior.

• Switches the sender to use a new HandleInternal interface method in place of HandleInbound for internal messages.
• Updates ChainRouter to implement HandleInternal and skip the allowlist check when routing internal messages.
• Adds tracing for internal message handling in tracedRouter and updates mocks and tests to use HandleInternal.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
snow/networking/sender/sender_test.go	Added subtests for validatorOnly flag and replaced HandleInbound expectations with HandleInternal.
snow/networking/sender/sender.go	Changed router interface to InternalHandler and replaced all go HandleInbound calls with HandleInternal.
snow/networking/router/traced_router.go	Implemented tracing in new HandleInternal method.
snow/networking/router/routermock/router.go	Added mock methods and recorders for HandleInternal.
snow/networking/router/router.go	Extended InternalHandler interface with HandleInternal.
snow/networking/router/chain_router.go	Implemented HandleInternal in ChainRouter and updated routing to skip allowlist for internal messages.

Comments suppressed due to low confidence (2)

snow/networking/router/chain_router.go:210

• [nitpick] The comment above HandleInternal mentions lock ordering but could be updated to better explain how internal messages are enqueued and how they differ from inbound messages.

func (cr *ChainRouter) HandleInternal(ctx context.Context, msg message.InboundMessage) {

snow/networking/sender/sender.go:120

• [nitpick] Switching from asynchronous go invocation to a synchronous call may block the sender if HandleInternal does not spawn its own goroutine. Ensure this synchronous path cannot cause deadlocks or long blocking.

		s.router.HandleInternal(ctx, inMsg)