Fix flaky pipe auto split IT

[Caideyipi]

Motivation

IoTDBPipeAutoSplitIT assumes that auto split always leaves both history and realtime pipes visible immediately after creation. In practice, the history snapshot pipe can finish and be auto-dropped very quickly when there is no historical data, so SHOW PIPE may only return the realtime pipe and the test fails with expected 2 but was 1.

Modifications

• Relax the auto split assertion to require the realtime pipe and reject the original unsplit pipe.
• Allow the history pipe to be absent after automatic completion/drop.
• Keep validating the history pipe's sink option when that history pipe is still visible.

Tests

• Passed: git diff --check -- integration-test/src/test/java/org/apache/iotdb/pipe/it/dual/treemodel/auto/basic/IoTDBPipeAutoSplitIT.java
• Not run successfully locally: IoTDBPipeAutoSplitIT#testSingleEnv. Maven/JVM failed during compilation on this machine due Windows page file/native memory exhaustion.