RFR: 8370839: Tests to verify peculiar Proxy dispatching behaviors

[Chen Liang]

java.lang.reflect.Proxy has some surprising behaviors associated with protected methods in Object and covariant/contravariant overrides in interfaces. Such behaviors should have tests, so that they are not accidentally perturbed in Proxy updates.

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Commit messages:
 - 8370839: Tests to verify peculiar Proxy dispatching behaviors

Changes: https://git.openjdk.org/jdk/pull/28023/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28023&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370839
  Stats: 230 lines in 2 files changed: 230 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28023.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28023/head:pull/28023

PR: https://git.openjdk.org/jdk/pull/28023