RFR: 8297736: test/jdk/java/foreign/TestMatrix.java is broken

Tue Nov 29 13:52:11 UTC 2022

- Fix tests that try to run `TestDowncall` which was split into TestDowncallScope and TestDowncallStack
- Fix use of obsolete system properties to control specilization
- Add test to run TestVarArgs in un-sampled mode.

Testing: Manual runs of TestMatrix.java (it's a manual test) on Windows and Linux (WSL).

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Commit messages:
 - Fix TestMatrix

Changes: https://git.openjdk.org/jdk/pull/11398/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11398&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297736
  Stats: 74 lines in 1 file changed: 33 ins; 0 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/11398.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11398/head:pull/11398

PR: https://git.openjdk.org/jdk/pull/11398