RFR: 8361211: C2: Final graph reshaping generates unencodeable klass constants

[Aleksey Shipilev]

See the bug for more investigation. I have tried to come up with an isolated test, but failed. So I am doing this change somewhat blindly, without a clear regression test. The investigation on the CTW points directly to this code, and I believe we should be more conservative in final graph reshaping. [JDK-8343206](https://bugs.openjdk.org/browse/JDK-8343206) added the assert for `ConNKlass`, which somehow does not trigger. I think it is safe to bail out of this transformation.

Also, this only plugs this particular leak. I think we should really be disabling the abstract/interface encoding optimization until C2 does not expose itself to this issue on more paths. There is [JDK-8343218](https://bugs.openjdk.org/browse/JDK-8343218) that we can re-open.

Additional testing:
 - [x] Linux x86_64 server fastdebug, a rare CTW failure does not reproduce anymore
 - [x] Linux x86_64 server fastdebug, `tier1`
 - [ ] Linux x86_64 server fastdebug, `all`
 - [ ] Linux AArch64 server fastdebug, `all`

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/26559/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26559&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361211
  Stats: 8 lines in 1 file changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26559.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26559/head:pull/26559

PR: https://git.openjdk.org/jdk/pull/26559