[Pipe] Move OPC UA sink to pipe library

[Caideyipi]

Description

This PR ports TimechoDB MR !6798 to the latest Apache IoTDB master.

Move OPC UA sink out of the server

• Move the OPC UA sink implementation and example into the new library-pipe reactor module.
• Remove OPC UA from the built-in Pipe plugin registry and DataNode dependencies.
• Build an isolated fat JAR and package Pipe library artifacts in a dedicated distribution ZIP.
• Register the external OPC UA plugin explicitly in integration tests.

Preserve shared behavior

• Share tablet-event transfer logic between the OPC DA sink and the external OPC UA sink.
• Preserve server/client reuse while guarding reference counts against failed customization and repeated close calls.
• Keep Milo dependency management local to library-pipe.

Apache compatibility

• Exclude TimechoDB-only initial-fetch and remote-sink features.
• Exclude private Maven coordinates, signing configuration, and branding.
• Update binary license information for the packaged Bouncy Castle dependency.

Validation

• mvn test -pl library-pipe/opc-ua-sink (19 tests)
• mvn verify -pl library-pipe/opc-ua-sink -DskipTests
• mvn test -pl iotdb-core/datanode -Dtest=PipeSinkTest,PipeSinkSubtaskManagerTest (23 tests)
• mvn test-compile -pl integration-test -P with-integration-tests -DskipTests (858 test sources)
• Fat JAR contents and signature metadata inspected

This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• added or updated license information.
• added unit tests or modified existing tests to cover new code paths.
• added integration test coverage.

Key changed/added classes (or packages if there are too many classes)

• library-pipe/opc-ua-sink
• PipeTabletEventTransferUtils
• BuiltinPipePlugin
• IoTDBPipeOPCUAIT
• distribution/src/assembly/library-pipe.xml