During upgrades from 7.x to 8.x if a node was holding a frozen cache file, the system considers that as an unknown file and prevents starting the node:
```
java.lang.IllegalStateException: unexpected file/folder encountered during data folder upgrade: /app/data/nodes/0/shared_snapshot_cache
	at org.elasticsearch.env.NodeEnvironment.upgradeLegacyNodeFolders(NodeEnvironment.java:443) ~[elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.env.NodeEnvironment.<init>(NodeEnvironment.java:290) ~[elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.node.Node.<init>(Node.java:388) ~[elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.node.Node.<init>(Node.java:277) ~[elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:234) ~[elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:234) ~[elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:358) [elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:166) [elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:157) [elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:77) [elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:112) [elasticsearch-cli-8.0.1.jar:8.0.1]
	at org.elasticsearch.cli.Command.main(Command.java:77) [elasticsearch-cli-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:122) [elasticsearch-8.0.1.jar:8.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:80) [elasticsearch-8.0.1.jar:8.0.1]
```
These files are expected files and should be ignored/accepted during the data folder upgrade.
server/src/main/java/org/elasticsearch/env/NodeEnvironment.java
* @param indexSettings settings for the index being deleted
     */
    public void deleteIndexDirectoryUnderLock(Index index, IndexSettings indexSettings, Consumer<Path[]> listener) throws IOException {
        final Path[] indexPaths = indexPaths(index);
        logger.trace("deleting index {} directory, paths({}): [{}]", index, indexPaths.length, indexPaths);
        listener.accept(indexPaths);
        IOUtils.rm(indexPaths);
        if (indexSettings.hasCustomDataPath()) {
            Path customLocation = resolveIndexCustomLocation(indexSettings.customDataPath(), index.getUUID());
            logger.trace("deleting custom index {} directory [{}]", index, customLocation);
            listener.accept(new Path[] { customLocation });
            IOUtils.rm(customLocation);
        }
    }
    /**
     * Tries to lock all local shards for the given index. If any of the shard locks can't be acquired
     * a {@link ShardLockObtainFailedException} is thrown and all previously acquired locks are released.
     *
     * @param index the index to lock shards for
     * @param lockTimeoutMS how long to wait for acquiring the indices shard locks
     * @return the {@link ShardLock} instances for this index.
     */
    public List<ShardLock> lockAllForIndex(
        final Index index,
        final IndexSettings settings,
        final String lockDetails,
        final long lockTimeoutMS
    ) throws ShardLockObtainFailedException {
        final int numShards = settings.getNumberOfShards();
        if (numShards <= 0) {