RFR: 8342303: Segfault in update_inherited_vtable: AppCDS, old bytecode, and redefineClasses [v6]

[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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Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:

  @coleenp comment - use RedefineClassHelper

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21667/files
  - new: https://git.openjdk.org/jdk/pull/21667/files/d4aeb920..7d062bf5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21667&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21667&range=04-05

  Stats: 51 lines in 6 files changed: 5 ins; 39 del; 7 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