SOLR-17631: fix TestStressThreadBackup w.r.t. CheckIndex.Level (#3495)

* fix TestStressThreadBackup w.r.t. CheckIndex.Level
* use CheckIndex.Level in TestSnapshotCoreBackup

Author: cpoerschke

solr/core/src/test/org/apache/solr/handler/TestSnapshotCoreBackup.java

@@ -20,6 +20,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Arrays;
+import org.apache.lucene.index.CheckIndex;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.IndexCommit;
 import org.apache.lucene.store.Directory;
@@ -453,7 +454,7 @@ private static void simpleBackupCheck(
     }
     try (Directory dir = FSDirectory.open(backup)) {
       // Lucene 10 changed CheckIndex levels from 0-3 to 1-3, so we use 1 (minimum level)
-      TestUtil.checkIndex(dir, 1, true, true, null);
+      TestUtil.checkIndex(dir, CheckIndex.Level.MIN_VALUE, true, true, null);
       try (DirectoryReader r = DirectoryReader.open(dir)) {
         assertEquals("numDocs in " + backup, numDocs, r.numDocs());
         if (null != expectedSegmentsFileName) {

solr/core/src/test/org/apache/solr/handler/TestStressThreadBackup.java

@@ -31,6 +31,7 @@
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import org.apache.lucene.index.CheckIndex;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.store.Directory;
@@ -334,7 +335,7 @@ private void validateBackup(final Path backup) throws IOException {
     final int numRealDocsExpected = Integer.parseInt(m.group());
 
     try (Directory dir = FSDirectory.open(backup)) {
-      TestUtil.checkIndex(dir, 0, true, true, null);
+      TestUtil.checkIndex(dir, CheckIndex.Level.MIN_LEVEL_FOR_SLOW_CHECKS, true, true, null);
       try (DirectoryReader r = DirectoryReader.open(dir)) {
         assertEquals(
             "num real docs in " + backup,