RFR: 8267952: async logging supports to dynamically change tags and decorators [v6]

[Xin Liu]

> Support dynamic reconfiguration for async logging. 2 unittests are provided.
> The regression test discovers a race condition in LogTagSet::log() even with
> synchronous logging. It's not MT-safe if context switch happens between the
> creation of LogDecorations  and LogOutputList::Iterator. fixed.

Xin Liu 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 ten additional commits since the last revision:

 - AsyncLogWrite::flush() uses a synchronization token and wait for completion.
   
   This patch serializes all flush() calls in one thread.
 - Merge branch 'master' into JDK-8267952
 - Revert "Use Atomic::load/store for decorators."
   
   This reverts commit f279f2639bc638a35ae6c716987feb22d36a2a07.
 - Revert "Fix VC++ warning C4099"
   
   This reverts commit 157a065876850df784d9e7c034e106f4532b607a.
 - Fix VC++ warning C4099
 - Use Atomic::load/store for decorators.
   
   This patch also installed a sanity check which will assert that
   LogOutput::_decorators is subset of LogDecocrations. It will disclose
   more information if the assertion fails.
 - Merge branch 'master' into JDK-8267952
 - Add comments in LogTagSet::log().
 - 8267952: async logging supports to dynamically change tags and decorators

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4408/files
  - new: https://git.openjdk.java.net/jdk/pull/4408/files/157a0658..ae3ae36d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4408&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4408&range=04-05

  Stats: 18757 lines in 334 files changed: 11361 ins; 6472 del; 924 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4408.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4408/head:pull/4408

PR: https://git.openjdk.java.net/jdk/pull/4408