RFR: 8267952: async logging supports to dynamically change tags and decorators [v3]

[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 three additional commits since the last revision:

 - 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/6e51b96e..4d2de713

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4408&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4408&range=01-02

  Stats: 21258 lines in 511 files changed: 15622 ins; 3201 del; 2435 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