RFR: 8284909: [JVMCI] remove remnants of AOT support

[Doug Simon]

[JDK-8264805](https://bugs.openjdk.java.net/browse/JDK-8264805) removed Graal from the JDK which included support for using Graal as an AOT compiler ([JDK-8166089](https://bugs.openjdk.java.net/browse/JDK-8166089)). There were few bits of support left behind that this PR removes.

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Commit messages:
 - removed remnants of JEP 295 support

Changes: https://git.openjdk.java.net/jdk/pull/8263/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8263&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284909
  Stats: 129 lines in 6 files changed: 0 ins; 129 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8263.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8263/head:pull/8263

PR: https://git.openjdk.java.net/jdk/pull/8263