RFR: 8305509: C1 fails "assert(k != nullptr) failed: illegal use of unloaded klass"

[Coleen Phillimore]

I tested the fix for JDK-8304743 on tier1-8, then did this refactoring which required a ciKlass::get_Klass() call that failed.  This fix reverts the refactoring.
Tested with tier4.

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Commit messages:
 - 8305509: C1 fails "assert(k != nullptr) failed: illegal use of unloaded klass"

Changes: https://git.openjdk.org/jdk/pull/13327/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13327&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305509
  Stats: 44 lines in 4 files changed: 15 ins; 24 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/13327.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13327/head:pull/13327

PR: https://git.openjdk.org/jdk/pull/13327