RFR: 8262323: do not special case JVMCI in tiered compilation policy

[Doug Simon]

This PR moves some Graal specific code from shared compilation policy code into JVMCI specific files and tunes it better for libgraal.

-------------

Commit messages:
 - 8262323: do not special case JVMCI in tiered compilation policy

Changes: https://git.openjdk.java.net/jdk/pull/2847/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2847&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262323
  Stats: 37 lines in 2 files changed: 11 ins; 16 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2847.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2847/head:pull/2847

PR: https://git.openjdk.java.net/jdk/pull/2847