Fix config region pipe privilege trimming

[Caideyipi]

Description

• Avoid falling back to the table privilege visitor when a tree/config plan is denied by tree privilege trimming.
• Preserve the trimmed plan between tree and table privilege visitor stages.
• Add regression coverage for unauthorized tree plans and partially trimmed tree plans.

Reproduction

A minimal reproduction is covered by PipeConfigTreePrivilegeParseVisitorTest#testSourcePrivilegeTrimDoesNotFallbackToTableDefaultForTreePlan:

• Give the pipe source user READ_SCHEMA only on root.db.device.**.
• Feed IoTDBConfigRegionSource a realtime tree config plan, e.g. SetTTLPlan(root.db2.device.measurement, 100).
• Before this fix, tree privilege trimming returns empty, but the table privilege visitor still runs and falls back to its default visitPlan, so the unauthorized tree plan is transferred instead of being skipped or rejected.
• For a partially matched tree plan such as SetTTLPlan(root.*.device.measurement, 100), the fixed flow keeps the trimmed plan as root.db.device.measurement.

Run the regression test with:

mvn -pl iotdb-core/node-commons -DskipTests install
mvn -pl iotdb-core/confignode -Dtest=PipeConfigTreePrivilegeParseVisitorTest#testSourcePrivilegeTrimDoesNotFallbackToTableDefaultForTreePlan -Dsurefire.failIfNoSpecifiedTests=false test

Tests

• mvn spotless:apply -pl iotdb-core/confignode
• mvn -pl iotdb-core/node-commons -DskipTests install
• mvn -pl iotdb-core/confignode -Dtest=PipeConfigTreePrivilegeParseVisitorTest -Dsurefire.failIfNoSpecifiedTests=false test