[lake/hudi] Add Hudi Flink union read log table IT

[fhan688]

Purpose

Linked issue: #3284

This PR adds integration tests for Hudi log table union read based on the Flink union read test base introduced in #3522.

The tests verify that Fluss can read tiered Hudi snapshot data together with newly appended Fluss log data for datalake-enabled log tables.

Brief change log

• Add FlinkUnionReadLogTableITCase for Hudi log table union read.
• Verify batch full-type reads for both partitioned and non-partitioned log tables.
• Verify union read after the tiering job is canceled and new Fluss log records are appended.
• Verify projection pushdown and partition filter pushdown.
• Verify streaming union read with partition discovery.
• Verify savepoint-based failover and restore for a streaming insert job reading from a Hudi-backed log table.
• Reuse the Hudi Flink union read test base from [lake/hudi] Add Flink union read test base for Hudi #3522 and enable checkpointing for the tiering job.

Tests

• mvn -pl fluss-lake/fluss-lake-hudi -Dcheckstyle.skip=true spotless:apply
• mvn -pl fluss-client,fluss-lake/fluss-lake-hudi -am -DskipITs -Dcheckstyle.skip=true -DfailIfNoTests=false test-compile
• mvn -pl fluss-lake/fluss-lake-hudi -am -DskipITs=false -Dcheckstyle.skip=true -DfailIfNoTests=false -Dtest=FlinkUnionReadLogTableITCase test

API and Format

No API or storage format changes.

Documentation

No documentation changes. This PR only adds integration test coverage.

[luoyuxia]

@fhan688 Thanks. LGTM