RFR: 8292961: [JVMCI] Access to j.l.r.Method/Constructor/Field for ResolvedJavaMethod/ResolvedJavaField

[Doug Simon]

Native Image needs to convert `ResolvedJavaMethod` objects to `java.lang.reflect.Executable` objects and `ResolvedJavaField` objects to `java.lang.reflect.Field` objects. This is currently done by digging into JVMCI internals with reflection. Instead, this functionality should be exposed by public JVMCI API which is what this PR does.

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Commit messages:
 - add API to convert ResolvedJava[Method|Field] to Method|Constructor|Field (GR-41976)

Changes: https://git.openjdk.org/jdk/pull/11146/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11146&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292961
  Stats: 37 lines in 2 files changed: 34 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/11146.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11146/head:pull/11146

PR: https://git.openjdk.org/jdk/pull/11146