RFR: 8297766: Remove UseMallocOnly development option [v2]

[Afshin Zafari]

> ### Description
> The UseMallocOnly development option was originally used to detect memory stomping bugs with Arena allocations when the JVM was first in development.
> 
> The option has had a few bugs and is not in general use. There are ideas to add another way of Arena canary checking.
> 
> ### Patch:
> All occurrences of UseMallocOnly are removed.
> 
> ### Tests:
> Local, gTests: resourceArea and Arena
> Mach5: tier1-5

Afshin Zafari has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - 8297766: Remove UseMallocOnly development option
 - 8297766: Remove UseMallocOnly development option
 - 8297766: Remove UseMallocOnly development option
 - UseMallocOnly instances are removed

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11456/files
  - new: https://git.openjdk.org/jdk/pull/11456/files/0ab592bd..6cdd0b70

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11456&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11456&range=00-01

  Stats: 17317 lines in 369 files changed: 3045 ins; 13746 del; 526 mod
  Patch: https://git.openjdk.org/jdk/pull/11456.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11456/head:pull/11456

PR: https://git.openjdk.org/jdk/pull/11456