[jdk25u] RFR: 8361211: C2: Final graph reshaping generates unencodeable klass constants

[Aleksey Shipilev]

Fixes another corner case with abstract/interface class encoding in C2. We would be disabling this optimization in JDK 25 eventually. The consensus so far that the this fix stands on its own, and gives us an additional safety now.

Additional testing:
 - [ ] Linux x86_64 server fastdebug, `all`

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Commit messages:
 - Backport e304d37996b075b8b2b44b5762d7d242169add49

Changes: https://git.openjdk.org/jdk25u/pull/128/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=128&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361211
  Stats: 11 lines in 1 file changed: 9 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk25u/pull/128.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/128/head:pull/128

PR: https://git.openjdk.org/jdk25u/pull/128