RFR: 8267952: async logging supports to dynamically change tags and decorators [v4]

[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 incrementally with one additional commit since the last revision:

  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.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4408/files
  - new: https://git.openjdk.java.net/jdk/pull/4408/files/4d2de713..f279f263

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4408&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4408&range=02-03

  Stats: 85 lines in 8 files changed: 71 ins; 5 del; 9 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