RFR: 8329655: Cleanup KlassObj and klassOop names after the PermGen removal

[Stefan Karlsson]

We have a few places that uses the terms `KlassObj` and `klassOop` when referring to Klasses. This is old code from before the PermGen removal, when Klasses also were Java objects.

These names tripped me up when I was reading the heap heapInspection.cpp and first though we were mixing the klass *mirror* objects and klass pointers in the hash code calculation:

   // An aligned reference address (typically the least
   // address in the perm gen) used for hashing klass
   // objects.
   HeapWord* _ref;
...
_ref = (HeapWord*) Universe::boolArrayKlassObj();
...
uint KlassInfoTable::hash(const Klass* p) {
  return (uint)(((uintptr_t)p - (uintptr_t)_ref) >> 2);
}


I propose that we rename these functions (and stop casting the Klass* to a (HeapWord*)).

Tested with serviceability/dcmd/gc/ClassHistogramTest.java but will run this through our lower tiers.

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Commit messages:
 - 8329655:  Cleanup KlassObj and klassOop names after the PermGen removal

Changes: https://git.openjdk.org/jdk/pull/18618/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18618&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329655
  Stats: 125 lines in 29 files changed: 0 ins; 2 del; 123 mod
  Patch: https://git.openjdk.org/jdk/pull/18618.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18618/head:pull/18618

PR: https://git.openjdk.org/jdk/pull/18618