RFR: 8318682: SA decoding of scalar replaced objects is broken

[Tom Rodriguez]

The changes for JDK-8287061 didn't update the SA decoding logic and there are other places where the decoding has gotten out of sync with HotSpot.  Some of them can't be tested because they are part of JVMCI but I've added a directed test for the JDK-8287061 code and a more brute force test that tries to decode everything.

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Commit messages:
 - Add missing files
 - 8318682: SA decoding of scalar replaced objects is broken

Changes: https://git.openjdk.org/jdk/pull/17407/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17407&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318682
  Stats: 416 lines in 13 files changed: 400 ins; 4 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/17407.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17407/head:pull/17407

PR: https://git.openjdk.org/jdk/pull/17407