[lworld] RFR: 8373826: [lworld] Test PreviewAutoSuppress fails since jimage change

[Jan Lahoda]

Fixing `test/langtools/tools/javac/diags/CheckExamples.java` (`test/langtools/tools/javac/diags/examples/PrimitivePatternMatching.java`) and `test/langtools/tools/javac/preview/PreviewAutoSuppress.java` tests.

Unfortunately, it is quite hard to make the tests work both with and without `-DDISABLE_PREVIEW_PATCHING=true` (could be done for `PreviewAutoSuppress.java`, but it is very hard to do sensible for `CheckExamples.java`), so given the future is `-DDISABLE_PREVIEW_PATCHING=true`, this change forces this option. (The practical impact of testing only this variant for these two tests is basically zero, I think. We have a different test that verifies all the combinations.)

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Commit messages:
 - Fixing test when running with -DDISABLE_PREVIEW_PATCHING=true (and forcing a run with this option).

Changes: https://git.openjdk.org/valhalla/pull/1813/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1813&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373826
  Stats: 8 lines in 4 files changed: 3 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/valhalla/pull/1813.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1813/head:pull/1813

PR: https://git.openjdk.org/valhalla/pull/1813