RFR: 8229517: Support for optional asynchronous/buffered logging [v9]

[Xin Liu]

> This patch provides a buffer to store asynchrounous messages and flush them to
> underlying files periodically.

Xin Liu has updated the pull request incrementally with two additional commits since the last revision:

 - Fix bugs/style/typo based on reviewers' feedbacks.
 - Accurate Decorations for AsyncLogging.
   
   A lightweight LogDecorationRef is created to keep LogDecorations at
   logging site. It uses refcnt to keep track multiple usage and
   automatically clean up. If no decorator is in use, no LogDecorationRef
   is created.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3135/files
  - new: https://git.openjdk.java.net/jdk/pull/3135/files/4cf4a57f..e2d6f9e0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=08
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=07-08

  Stats: 207 lines in 12 files changed: 152 ins; 21 del; 34 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3135.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3135/head:pull/3135

PR: https://git.openjdk.java.net/jdk/pull/3135