[hongzhi-gao]

Description

Snapshot recovery without snapshot.log maintains a separate hard-link/copy branch. If the filesystem throws UnsupportedOperationException, recovery fails instead of copying the file. Its copy path also bypasses the force/error handling already used by logged snapshots.

Use the existing SnapshotFileUtils.createLinkOrCopy for this path, keeping directory selection and file-target registration unchanged. Add a regression that rejects hard links, restores the bytes by copying, deletes the source, and verifies the restored contents and target mapping. Add the JDK 17 test JVM opens required by the existing PowerMock fault injection. Explicitly declare the already-transitive powermock-api-support test dependency used by method replacement so dependency analysis passes.

Validation:

• mvn verify -o -pl iotdb-core/datanode -am -DskipTests -Ddevelocity.off=true: passed, including dependency:analyze-only with no dependency problems.
• mvn spotless:apply -o -pl iotdb-core/datanode -Ddevelocity.off=true: passed.
• mvn test -o -pl iotdb-core/datanode -am '-Dtest=SnapshotFileUtilsTest,SnapshotLinkFallbackTest,IoTDBSnapshotTest' -Dsurefire.failIfNoSpecifiedTests=false -DfailIfNoTests=false -Ddevelocity.off=true: 15 passed, 1 pre-existing ignored test.
• Cluster migration and crash-injection tests were not run.

This PR has:

• been self-reviewed.
• added a regression test for the changed recovery path.

Key changed classes: SnapshotLoader, SnapshotLinkFallbackTest.

[Caideyipi]

Reviewed the current head. The unsupported hard-link case now uses the shared copy fallback, and the regression test checks restored contents after deleting the source. No code issues found.