Support target database in write-back sink

[Caideyipi]

Changes

• Add sink.database / connector.database support for write-back sink data writes.
• Validate write-back sink database names on the sink side instead of relying on generic path validation.
• Use table-model create-database validation for table-model database names.
• Use tree-model create-database validation semantics for tree-model database names, including root. requirement, legal tree path parsing, database-name pattern check, and length limit.
• Support multi-level tree-model target databases such as root.target.db.
• Reject table-model writes when the event or target mapping produces an invalid table-model database, for example tree database root.a.b mapping to table database a.b.
• Rewrite target database for both table-model and tree-model insertion statements.
• Add UT coverage for target database validation boundaries, target database customization/mapping, raw tablet event rejection, and statement event rejection.
• Update tree-model write-back sink IT coverage to use a multi-level target database.

Semantics

• sink.database=target is treated as a table-model database and mapped to tree database root.target for tree writes.
• sink.database=root.target and sink.database=root.target.db are treated as tree-model databases.
• A multi-level tree-model database such as root.target.db is valid for tree-model writes.
• The corresponding table-model database name for root.target.db is target.db, which is invalid in table model and must reject table-model events.
• Table-model events always validate their event database name with table-model create-database rules before applying a configured target database, so source values like root.a.b / a.b are rejected.
• Tree-model events always validate their event database name with tree-model create-database rules before applying a configured target database.

Validation

• mvn spotless:apply -pl iotdb-core/datanode
• mvn spotless:apply -pl integration-test -P with-integration-tests
• git diff --check
• mvn -pl iotdb-core/datanode -Dtest=PipeSinkTest test was attempted, but datanode compilation fails before test execution in existing generated Freemarker sources unrelated to this change, including missing IFill, IFillFilter, LinearFill, Accumulator, org.apache.commons.collections4.comparators, and IoTDBConfig#getModeMapSizeThreshold().

[jt2594838]

When will this happen?