[jdk21u-dev] RFR: 8336635: Add IR test for Reference.refersTo intrinsic

[Michael De Vera]

Backport of JDK-8336635. Adds test to confirm Reference.refersTo intrinsics are properly handled. 

https://bugs.openjdk.org/browse/JDK-8336635

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Commit messages:
 - Backport c73b3cb5996723c5a15c833a9da059b79c99cf9c

Changes: https://git.openjdk.org/jdk21u-dev/pull/1864/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1864&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336635
  Stats: 156 lines in 1 file changed: 156 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1864.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1864/head:pull/1864

PR: https://git.openjdk.org/jdk21u-dev/pull/1864