[jdk17u-dev] RFR: 8314120: Add tests for FileDescriptor.sync

[Michael De Vera]

Backport of JDK-8317788 to add sanity tests for FileDescriptor.Sync. Not clean, but trivial fix to remove case which tested using virtual threads. New tests passing on x64 linux.

% make test TEST="micro:java.io.FileDescriptorSync"

==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR   
   micro:java.io.FileDescriptorSync                      1     1     0     0   
==============================
TEST SUCCESS

% make test TEST="java/io/FileDescriptor/Sync.java" 
==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR   
   jtreg:test/jdk/java/io/FileDescriptor/Sync.java       1     1     0     0   
==============================
TEST SUCCESS

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

Commit messages:
 - Remove VThread test case
 - Backport e22d333febe9edbb961fee9b51759d4cd28684fd

Changes: https://git.openjdk.org/jdk17u-dev/pull/3516/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3516&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314120
  Stats: 160 lines in 2 files changed: 160 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3516.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3516/head:pull/3516

PR: https://git.openjdk.org/jdk17u-dev/pull/3516