RFR: 8296960: [JVMCI] list HotSpotConstantPool.loadReferencedType to ConstantPool

[Doug Simon]

`HotSpotConstantPool.loadReferencedType(int cpi, int opcode, boolean initialize)` allows loading a type without triggering class initialization. This PR lifts this method up to `ConstantPool` so that this functionality can be used without depending on HotSpot-specific JVMCI classes.

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Commit messages:
 - lift loadReferencedType with initialize parameter up to ConstantPool (GR-41975)

Changes: https://git.openjdk.org/jdk/pull/11145/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11145&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296960
  Stats: 19 lines in 2 files changed: 19 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11145.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11145/head:pull/11145

PR: https://git.openjdk.org/jdk/pull/11145