RFR: 8337213: Shenandoah: Add verification for class mirrors

[Aleksey Shipilev]

When working in Leyden, I noticed some oddities when loading Class mirrors from the CDS archive. These are not caught by Shenandoah asserts or verifier, since the problem is due to wrong metadata. We can amend verification to test these. 

Additional testing:
 - [ ] Linux x86_64 server fastdebug, `all` with `-XX:+UseShenandoahGC`

-------------

Commit messages:
 - Advanced verify

Changes: https://git.openjdk.org/jdk/pull/20332/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20332&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337213
  Stats: 34 lines in 2 files changed: 34 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20332.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20332/head:pull/20332

PR: https://git.openjdk.org/jdk/pull/20332