RFR: 8266973: Migrate to ClassHierarchyIterator when enumerating subclasses [v2]

[Vladimir Ivanov]

> Replace ad-hoc recursion when enumerating subclasses with `ClassHierarchyIterator`.
> 
> Found 3 occurrences:
> - `Dependencies::find_finalizable_subclass()`
> - `reinitialize_vtable_of()`
> - `VM_RedefineClasses::increment_class_counter()`
> 
> Testing:
> - [x] hs-tier1 - hs-tier4

Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  JFR

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3995/files
  - new: https://git.openjdk.java.net/jdk/pull/3995/files/cb586871..54a4bddd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3995&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3995&range=00-01

  Stats: 46 lines in 2 files changed: 1 ins; 35 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3995.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3995/head:pull/3995

PR: https://git.openjdk.java.net/jdk/pull/3995