more resilient segment cache legacy path file moves during startup

[clintropolis]

Description

Follow up to #18176, which moved segment cache files from being stored in deeply nested paths of the form {location}/{datasource}/ {interval}/{version}/{partition}/ to being stored in a flatly in the location using the segmentId as the path and includes some logic to move the files from the old paths to the new paths on startup.

This PR improves the file legacy segment cache file location move logic which lives in SegmentLocalCacheManager.getCachedSegments to be more resilient in cases where startup is interrupted and cases where files exist in both locations due to upgrade/downgrade/upgrade cycles.

The added test covers the latter scenario, and would fail with something like

025-09-04T22:11:47,199 ERROR [main] org.apache.druid.segment.loading.SegmentLocalCacheManager - Failed to load segment from segment cache file.: {exceptionType=java.nio.file.DirectoryNotEmptyException, exceptionMessage=/var/folders/8y/mhfmxp391pl9m2h103s_kn200000gn/T/junit6723303392002826755/segment_cache/test_segment_loader_2011-01-12T00:00:00.000Z_2011-04-15T00:00:00.001Z_2015-05-27T03:38:35.683Z, class=org.apache.druid.segment.loading.SegmentLocalCacheManager, file=/var/folders/8y/mhfmxp391pl9m2h103s_kn200000gn/T/junit6723303392002826755/segment_cache/info_dir/test_segment_loader_2011-01-12T00:00:00.000Z_2011-04-15T00:00:00.001Z_2015-05-27T03:38:35.683Z}
java.nio.file.DirectoryNotEmptyException: /var/folders/8y/mhfmxp391pl9m2h103s_kn200000gn/T/junit6723303392002826755/segment_cache/test_segment_loader_2011-01-12T00:00:00.000Z_2011-04-15T00:00:00.001Z_2015-05-27T03:38:35.683Z
	at java.base/sun.nio.fs.UnixFileSystem.move(UnixFileSystem.java:927) ~[?:?]
	at java.base/sun.nio.fs.UnixFileSystemProvider.move(UnixFileSystemProvider.java:309) ~[?:?]
	at java.base/java.nio.file.Files.move(Files.java:1431) ~[?:?]
	at org.apache.druid.segment.loading.SegmentLocalCacheManager.getCachedSegments(SegmentLocalCacheManager.java:217) [classes/:?]

without the changes in this PR