fix(net): gate peer traffic on hello validation and enforce timeout

[317787106]

What does this PR do?

Require a validated application-layer HELLO before processing peer traffic, enforce a handshake deadline, and validate untrusted HELLO fields before formatting logs.

• Before HELLO validation succeeds, allow only HELLO and DISCONNECT. Reject other message types with BAD_PROTOCOL before parsing or PBFT dispatch, and reject null or empty frames safely.
• Add a 10-second HELLO timeout based on the local channel start time, independent of synchronization flags or recent peer activity. Use the existing status-check cycle and TIME_OUT disconnect, while retaining synchronization and request timeout checks. Make helloMessageReceive volatile for visibility to the status-check thread.
• Extract validEndPoint() to validate the raw protobuf endpoint: port 1–65535, at least one IP address, a 200-byte limit per address field, and valid IPv4/IPv6 literals for every nonempty field. Run validation before toString() constructs a Node; preserve the log format for valid HELLO messages.
• For invalid HELLO messages, log the three block-hash lengths and an endpointValid flag instead of full hashes. Read diagnostic lengths with ByteString.size() to avoid copying untrusted fields for logging.

Why are these changes required?

Peers could reach business handlers, including PBFT, before completing the application handshake, while handshake timeout depended indirectly on synchronization state. Malformed endpoint fields could also reach address formatting before validation, and oversized hashes could produce excessive warning output.

Handshake admission retains the existing version, genesis, and solid-block compatibility checks without adding a main-chain membership requirement for the peer's unfinalized head. This avoids rejecting otherwise compatible peers during a temporary fork, including reconnection after a disconnect or restart. Subsequent fork handling remains with the existing synchronization and broadcast logic.

This PR has been tested by:

• Focused unit tests and regressions on ARM64 / JDK 17 covering message gating, endpoint validation, bounded logging, handshake compatibility, peer connections, and timeouts.
• Logging scenarios consolidated into HandShakeServiceTest; HELLO timeout scenarios consolidated into PeerStatusCheckMockTest. The latest timeout consolidation passed 24 related tests.
• HelloMessageTest.testValidAddressLogFormat verified on an actual Java 8 runtime after fixing its JDK-dependent IPv6 formatting expectation.
• ./gradlew checkstyleMain checkstyleTest and git diff --check passed locally.

The full repository test suite and manual multi-node network testing were not run locally.

Follow up

The planned libp2p v2.3.0 fixes will be integrated into java-tron separately. This PR covers java-tron's application-layer HELLO handling and does not update the libp2p dependency.

Extra details

• Ten seconds is the timeout threshold; disconnection occurs on the existing periodic status-check cycle.
• No changes to the wire format, configuration, or fork-choice logic are introduced. The implementation remains Java 8 compatible.

[3for]

LGTM now.