[foreign-abi] RFR: Nio benchmark [v2]

[Henry Jen]

> This added a simple benchmark to get DirectoryStream implemented with Panama, compared to a simplified JNI version also
> the stock implementation. Currently MacOS and Linux are included, for other platform, default kicks in and abort with
> exception.  To enable platform dependant code needed by Panama, we add a folder, test/os, where we can put platform
> override implementation. This allows minimum change to the code layout, however, the colocation is less than desired.
> Support package of jdk.incubator.jbind.core is added, as that's what needed for jbind generated code. This is basically
> what jextract generated RuntimeHelper.
> LibC.java is generated by jbind. The command used to generate the file is gencode.sh, the patch also contains argument
> files.
> When generate code with jbind, there are redundant files no needed for the benchmark, use `git status` to identify
> those and it's safe to remove them and only keep the LibC.java.

Henry Jen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains
24 commits:

 - Merge remote-tracking branch 'openjdk/foreign-abi' into NioBenchmark
 - 8249879: Split MemorySegment and MemoryAddress (linux test fix)
 - 8249879: Split MemorySegment and MemoryAddress (test fix)
 - Merge branch 'foreign-abi' of https://github.com/openjdk/panama-foreign into NioBenchmark
 - Merge branch 'foreign-abi' of https://github.com/openjdk/panama-foreign into NioBenchmark
 - Merge branch 'foreign-abi' of https://github.com/openjdk/panama-foreign into NioBenchmark
 - Adapt Addressable
 - Merge branch 'foreign-abi' of https://github.com/openjdk/panama-foreign into NioBenchmark
 - Merge branch 'NioBenchmark' of github.com:slowhog/panama-foreign into NioBenchmark
 - Merge branch 'foreign-abi' of https://github.com/openjdk/panama-foreign into NioBenchmark
 - ... and 14 more: https://git.openjdk.java.net/panama-foreign/compare/0cf5d863...77f42b13

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

Changes: https://git.openjdk.java.net/panama-foreign/pull/278/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/278/webrev.01
  Stats: 2426 lines in 26 files changed: 2424 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/278.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/278/head:pull/278

PR: https://git.openjdk.java.net/panama-foreign/pull/278