Fix empty deleteTimeseries requests

[Caideyipi]

Summary

• Treat empty deleteTimeseries path lists as no-op in SessionConnection and SessionPool.
• Return SUCCESS for empty deleteTimeseries thrift requests after login validation.
• Add regression coverage for Session and SessionPool empty-list calls.

Fixes #11612

Tests

• git diff --check
• mvn "-Ddevelocity.off=true" -pl iotdb-client/session "-Dtest=SessionConnectionTest#testDeleteEmptyTimeseries,SessionPoolTest#testDeleteEmptyTimeseriesList" test

Notes

• Tried datanode compile with: mvn "-Ddevelocity.off=true" -pl iotdb-core/datanode -DskipTests compile
• That local compile fails on unrelated existing dependency/generated-source mismatches such as missing IOUtils.readFully, parser symbols, and freemarker aggregation dependencies.