feat: Add 2 outbound block-relay-only connections

[zhangsoledad]

What is changed and how it works?

This approach was motivated by the TxProbe paper.，After this PR, CKB will make 2 additional outbound connections that are only used for block relay.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Side effects

• Performance regression
• Breaking backward compatibility

Release note

Title Only: Include only the PR title in the release note.

[Copilot]

Pull Request Overview

This PR implements the new feature of adding two outbound block‐relay-only connections. Key changes include adding a new config flag (disable_block_relay_only_connection), updating peer registry logic to support block relay only sessions, and propagating these changes through tests, protocols, and peer store modules.

Reviewed Changes

Copilot reviewed 20 out of 21 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
util/light-client-protocol-server/src/tests/utils/network_context.rs	Added stub for full_relay_connected_peers in test context.
util/app-config/src/configs/network.rs	Introduced a new configuration flag for disabling block‐relay-only connections.
test/src/specs/p2p/whitelist.rs	Updated whitelist tests to disable block‐relay‐only connections.
sync/*	Added implementations for full_relay_connected_peers in various test modules.
network/src/protocols/*	Updated protocol implementations to use the full_relay_connected_peers API and change the register method signature to return a bool.
network/src/peer_store/*	Integrated anchors support into peer store for managing block‐relay‐only peers.
network/src/peer_registry.rs	Updated peer acceptance logic and connection status counters to handle block‐relay‐only sessions.
network/src/peer.rs	Introduced a new SessionType enum with a BlockRelayOnly variant.
network/src/network.rs	Updated network initialization to include anchors for block‐relay‐only peers.
network/src/lib.rs	Adjusted imports to align with the new session type and protocol changes.

Comments suppressed due to low confidence (1)

network/src/protocols/identify/mod.rs:364

• Update the documentation comment for the register method to reflect that it now returns a bool indicating whether registration succeeded, so that future readers and integrators clearly understand this API change.

    fn register(&self, context: &ProtocolContextMutRef, version: &str) -> bool {