Implement UDP transport for air-gap sink

[Caideyipi]

Summary

• Add tcp/udp transport option and UDP packet size validation for air-gap connector/sink.
• Send UDP air-gap datagrams with the existing envelope/ACK flow and slice oversized requests.
• Make the receiver listen on UDP on the air-gap port and keep per UDP client receiver/session state.

Tests

• mvn -DskipTests spotless:apply -pl iotdb-core/node-commons,iotdb-core/datanode
• mvn -pl iotdb-core/node-commons -DskipTests compile
• git diff --check
• mvn -pl iotdb-core/datanode -Dtest=IoTDBDataRegionAirGapSinkTest,IoTDBAirGapReceiverTest test (fails during existing datanode compilation: missing parser/generated/calc/consensus symbols such as AlterTopicContext, ComparatorChain, PERCENTILE, and IStateMachine.loadSnapshot return mismatch)

[codecov]

Codecov Report

❌ Patch coverage is 55.41126% with 103 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.10%. Comparing base (89d4fbb) to head (0edcf5f).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...iver/protocol/airgap/IoTDBAirGapReceiverAgent.java	5.76%	49 Missing ⚠️
.../receiver/protocol/airgap/IoTDBAirGapReceiver.java	35.29%	33 Missing ⚠️
...db/commons/pipe/sink/protocol/IoTDBAirGapSink.java	84.61%	18 Missing ⚠️
...er/protocol/thrift/IoTDBDataNodeReceiverAgent.java	62.50%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #17954      +/-   ##
============================================
+ Coverage     43.91%   44.10%   +0.19%     
  Complexity      377      377              
============================================
  Files          5406     5406              
  Lines        389355   389557     +202     
  Branches      50871    50896      +25     
============================================
+ Hits         170974   171809     +835     
+ Misses       218381   217748     -633     

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[sonarqubecloud]

Quality Gate passed

Issues
9 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
2.4% Duplication on New Code

See analysis details on SonarQube Cloud