RFR: 8318682: SA decoding of scalar replaced objects is broken [v6]

[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.

Tom Rodriguez has updated the pull request incrementally with one additional commit since the last revision:

  Review comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17407/files
  - new: https://git.openjdk.org/jdk/pull/17407/files/07eefccd..f25c92ef

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17407&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17407&range=04-05

  Stats: 5 lines in 1 file changed: 0 ins; 4 del; 1 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