RFR: 8289687: [JVMCI] bug in HotSpotResolvedJavaMethodImpl.equals

[Doug Simon]

A bug[1] slipped in with [JDK-8289094](https://bugs.openjdk.org/browse/JDK-8289094) that broke `HotSpotResolvedJavaMethodImpl.equals`.This PR fixes and adds a test for it. The test was added to `TestResolvedJavaMethod` which was disabled (see [JDK-8249621](https://bugs.openjdk.org/browse/JDK-8249621)). This test class has been re-enabled and the 2 other failing tests in it (`canBeStaticallyBoundTest` and `asStackTraceElementTest`) have been fixed.

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Commit messages:
 - fixed jdk.vm.ci.hotspot.HotSpotResolvedJavaMethodImpl.equals(Object)

Changes: https://git.openjdk.org/jdk/pull/9364/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9364&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289687
  Stats: 67 lines in 5 files changed: 40 ins; 1 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/9364.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9364/head:pull/9364

PR: https://git.openjdk.org/jdk/pull/9364