[foreign-abi] RFR: Nio benchmark

[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.

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

Commit messages:
 - 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
 - Add Linux benchmark
 - ... and 13 more: https://git.openjdk.java.net/panama-foreign/compare/c342261a...7dd2399f

Changes: https://git.openjdk.java.net/panama-foreign/pull/278/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/278/webrev.00
  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