[jdk17u-dev] RFR: 8331885: C2: meet between unloaded and speculative types is not symmetric

[Martin Doerr]

Backport of [JDK-8331885](https://bugs.openjdk.org/browse/JDK-8331885). Manual integration was needed. I had to omit `_interfaces` in `TypeInstPtr::with_speculative` because [JDK-8297933](https://bugs.openjdk.org/browse/JDK-8297933) is not in 17u. The context differs to some degree, but all modified lines of code match. Please review!

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

Commit messages:
 - Backport 7652f9811bfddf08650b0c3277012074873deade

Changes: https://git.openjdk.org/jdk17u-dev/pull/2554/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2554&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331885
  Stats: 20 lines in 3 files changed: 12 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2554.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2554/head:pull/2554

PR: https://git.openjdk.org/jdk17u-dev/pull/2554