[jdk11u-dev] RFR: 8223050: JVMCI: findUniqueConcreteMethod() should not use Dependencies::find_unique_concrete_method() for non-virtual methods

[Severin Gehwolf]

Please review this backport of JDK-8223050 related to JVMCI. The JDK 13 patch doesn't apply cleanly. The change in assert in check_unique_method() has been left out since JDK 11u doesn't have [JDK-8223171](https://bugs.openjdk.java.net/browse/JDK-8223171) which introduced this method. It doesn't seem needed to bring that in too. JVMCI_THROW_MSG_NULL doesn't exist in JDK 11u. I've used THROW_MSG_0 instead. Finally, test `TestResolvedJavaMethod.java` needed to account for this change as it would fail otherwise. Note that the test is `@ignored` in HEAD so hasn't been fixed there.

**Testing**

- [x] tier1 on Linux x86_64 (pass)
- [x] `jtreg:test/hotspot/jtreg/compiler/jvmci/` most notably `FindUniqueConcreteMethodTest.java` and `TestResolvedJavaMethod.java`. All pass.

Thoughts?

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Commit messages:
 - Backport c18ffd6a79fc6cd634b410a2dd37d0026ebb2664

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/48/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=48&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8223050
  Stats: 42 lines in 4 files changed: 30 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/48.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/48/head:pull/48

PR: https://git.openjdk.java.net/jdk11u-dev/pull/48