RFR: 8344911: Introduce test utility for asserting file open status [v2]

[Eirik Bjørsnøs]

> Please review this PR which  adds a utility API in the test libraries to assert whether a file is currently open.
> 
> Several OpenJDK  tests currently rely on approximations to check this, including deletion (fails only on Windows), or checking `/proc/<pid>/fd` (Works only on Linux). These approximations are blunt instruments, it would be better to have an exact cross platform solution for this need to check if a file is open or closed.
> 
> Initial support includes:
> 
> * `FileInputStream`, `FileOutputStream` and `RandomAccessFile` from `java.io`
> * `FileChannelImpl` from `java.nio`, meaning we can check synchronous NIO APIs such as `Files.newInputStream`, `Files.newOutputStream`, `Files.newByteChannel` and `FileChannel.open`
> 
> This allows testing of many (most?) JDK APIs such as `ZipFile`, `JarFile`, `JarURLConnection`, `FileURLConnection` etc.
> 
> Tests use the following configuration to enable  instrumentation of file access APIs:
> 
> 
> * @library /test/lib
> * @run driver jdk.test.lib.util.OpenFilesAgent
> * @run junit/othervm -javaagent:OpenFilesAgent.jar OpenFilesTest
> 
> 
> Also provided is an assertion API to verify whether files are open or not:
> 
> 
> Path file = Files.createFile(Path.of("file.txt"));
> assertClosed(file);
> try (var is = Files.newInputStream(file)) {
>     assertOpen(file);
> }
> assertClosed(file);
> ``` 
> 
> A failed `assertClosed` shows the stack trace for whatever action opened the file:
> 
> 
> Caused by: java.lang.Throwable: Opening stack trace of jdk/build/macosx-x86_64-server-release/JTwork/scratch/file.txt
> 	at jdk.test.lib.util.OpenFiles.openFile(OpenFiles.java:59)
> 	at java.base/java.nio.file.Files.newByteChannel(Files.java:357)
> 	at java.base/java.nio.file.Files.newByteChannel(Files.java:399)
> 	at java.base/java.nio.file.spi.FileSystemProvider.newInputStream(FileSystemProvider.java:371)
> 	at java.base/java.nio.file.Files.newInputStream(Files.java:154)
> 	at OpenFilesTest.sample(OpenFilesTest.java:81)
> 
> 
> See the library implementation test `OpenFilesTest` for samples.
> 
> Verification:
> With `OpenFilesTest` temporarily in tier1, GHA completed successfully across platforms.

Eirik Bjørsnøs has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Test infrastructure to assert that a file is open or closed

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/22343/files
  - new: https://git.openjdk.org/jdk/pull/22343/files/0cfc3ad0..abc2d2fe

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22343&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22343&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22343.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22343/head:pull/22343

PR: https://git.openjdk.org/jdk/pull/22343