RFR: 8342303: Segfault in update_inherited_vtable: AppCDS, old bytecode, and redefineClasses

[Calvin Cheung]

A simple fix to avoid referencing invalid vtable and itable entires in `InstanceKlass::restore_unshareable_info` if a class is not linked during CDS dump time.

Passed tiers 1 - 4 testing.

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Commit messages:
 - new fix
 - 8342303: Segfault in update_inherited_vtable: AppCDS, old bytecode, and redefineClasses

Changes: https://git.openjdk.org/jdk/pull/21667/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21667&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342303
  Stats: 155 lines in 4 files changed: 152 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21667.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21667/head:pull/21667

PR: https://git.openjdk.org/jdk/pull/21667