Improve exception readability in case a directory can't be deleted because it still contains files

[Vlatombe]

Found this while investigating a test flake report and realized the current reported exception was a bit confusing.

So, proposing this:

Use suppressed exceptions rather than wrap the exception so that we get the primary cause first, then details.

Also resolve files relative to their containing folders.

Before:

java.io.IOException: [REDACTED]/target/tmp/j h16565971146678333138/users/Fred_10744520479289247763/config.xml
	at org.jvnet.hudson.test.TemporaryDirectoryAllocator.delete(TemporaryDirectoryAllocator.java:144)
	at org.jvnet.hudson.test.TemporaryDirectoryAllocator.delete(TemporaryDirectoryAllocator.java:131)
	at org.jvnet.hudson.test.TemporaryDirectoryAllocator.delete(TemporaryDirectoryAllocator.java:131)
	at org.jvnet.hudson.test.TemporaryDirectoryAllocator.dispose(TemporaryDirectoryAllocator.java:99)
	at org.jvnet.hudson.test.TestEnvironment.dispose(TestEnvironment.java:84)
	at org.jvnet.hudson.test.JenkinsRule.after(JenkinsRule.java:527)
	at org.jvnet.hudson.test.JenkinsRule$1.evaluate(JenkinsRule.java:665)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: java.nio.file.DirectoryNotEmptyException: [REDACTED]/target/tmp/j h16565971146678333138/users/Fred_10744520479289247763
	at java.base/sun.nio.fs.UnixFileSystemProvider.implDelete(UnixFileSystemProvider.java:246)
	at java.base/sun.nio.fs.AbstractFileSystemProvider.deleteIfExists(AbstractFileSystemProvider.java:110)
	at java.base/java.nio.file.Files.deleteIfExists(Files.java:1191)
	at org.jvnet.hudson.test.TemporaryDirectoryAllocator.delete(TemporaryDirectoryAllocator.java:141)
	... 8 more

After:

java.nio.file.DirectoryNotEmptyException: [REDACTED]/target/tmp/j h16565971146678333138/users/Fred_10744520479289247763
        at java.base/sun.nio.fs.UnixFileSystemProvider.implDelete(UnixFileSystemProvider.java:289)
        at java.base/sun.nio.fs.AbstractFileSystemProvider.deleteIfExists(AbstractFileSystemProvider.java:109)
        at java.base/java.nio.file.Files.deleteIfExists(Files.java:1191)
        at org.jvnet.hudson.test.TemporaryDirectoryAllocator.delete(TemporaryDirectoryAllocator.java:142)
        at org.jvnet.hudson.test.TemporaryDirectoryAllocator.dispose(TemporaryDirectoryAllocator.java:100)
        at org.jvnet.hudson.test.TestEnvironment.dispose(TestEnvironment.java:84)
        at org.jvnet.hudson.test.JenkinsRule.after(JenkinsRule.java:586)
        at org.jvnet.hudson.test.JenkinsRule$1.evaluate(JenkinsRule.java:724)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
        at java.base/java.lang.Thread.run(Thread.java:1583)
        Suppressed: java.io.IOException: These files still exist : config.xml
                at org.jvnet.hudson.test.TemporaryDirectoryAllocator.delete(TemporaryDirectoryAllocator.java:146)
                ... 6 more

Manually tested with the following patch to produce non-empty directories.

Index: src/main/java/org/jvnet/hudson/test/TemporaryDirectoryAllocator.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/src/main/java/org/jvnet/hudson/test/TemporaryDirectoryAllocator.java b/src/main/java/org/jvnet/hudson/test/TemporaryDirectoryAllocator.java
--- a/src/main/java/org/jvnet/hudson/test/TemporaryDirectoryAllocator.java	(revision 3b5659834a066c27a991c742649d976b535dc18a)
+++ b/src/main/java/org/jvnet/hudson/test/TemporaryDirectoryAllocator.java	(date 1723541060918)
@@ -126,13 +126,6 @@
 
     private void delete(Path p) throws IOException {
         LOGGER.fine(() -> "deleting " + p);
-        if (Files.isDirectory(p, LinkOption.NOFOLLOW_LINKS)) {
-            try (DirectoryStream<Path> children = Files.newDirectoryStream(p)) {
-                for (Path child : children) {
-                    delete(child);
-                }
-            }
-        }
         try {
             if (isWindows()) {
                 // Windows throws an access denied exception when deleting read-only files

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[MarkEWaite]

Thanks!