Add degraded status to show pipes

[Caideyipi]

Summary

• Add nullable degraded-state visibility to pipes: IsDegraded in SHOW PIPES, is_degraded in information_schema.pipes, and matching Thrift fields.
• Propagate degraded state from DataNodes to ConfigNodes through pipe heartbeat metadata with tri-state encode/decode support, so missing data remains unknown instead of being treated as false.
• Track degraded realtime extraction in PipeRealtimeDataRegionHybridSource by marking active TsFile epochs degraded when extraction has to use the TsFile/BOTH path after tablet data becomes unreliable, and clearing the status when the epoch is no longer active.
• Aggregate per-region status on DataNodes and per-node status on ConfigNodes so any degraded region/node makes the pipe degraded, all known false values make it non-degraded, and no known values remain unknown.

Test Coverage

• PipeTemporaryMetaTest covers the tri-state codec plus DataNode/ConfigNode aggregation.
• PipeHeartbeatParserTest covers heartbeat propagation, aggregation across DataNodes, and missing degraded heartbeat values.
• PipeTableRespTest and ShowPipeTaskTest cover SHOW PIPES output.
• PipeRealtimeExtractTest covers hybrid source degraded reporting and cleanup.

Local Checks

• git diff --check
• mvn spotless:apply -pl iotdb-core/confignode
• mvn test -pl iotdb-core/node-commons -Dtest=PipeTemporaryMetaTest '-Dcheckstyle.skip=true'