RFR: 8275439: Remove PrintVtableStats

[Zhengyu Gu]

PrintVtableStats has not been very useful and reported information may not be accurate neither. Please see the CR and comments in JDK-8275413 for details.

- PrintVtableStats is none product flag, so does not require a CSR to remove it.
- The patch also removes Klass::array_klasses_do() and families, as PrintVtableStats is the last use.
- InstanceKlass/ArrayKlass::array_klasses_do(void f(Klass* k, TRAPS), TRAPS) have no use, remove them as well.

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Commit messages:
 - v0

Changes: https://git.openjdk.java.net/jdk/pull/6017/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6017&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275439
  Stats: 125 lines in 9 files changed: 0 ins; 125 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6017.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6017/head:pull/6017

PR: https://git.openjdk.java.net/jdk/pull/6017