RFR: 8229517: Support for optional asynchronous/buffered logging [v18]

[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 one additional commit since the last revision:

  Add threadump support for AsyncLog Thread.
  
  when jstack requests to dump threads:
  "AsyncLog Thread" os_prio=0 cpu=239.26ms elapsed=52.13s tid=0x00007fb814c76ec0 nid=0x9023 runnable
  
  When jvm crash, thread dump is written to hs_err_pid$pid.log.
  0x00007fa8d824e450 Thread "AsyncLog Thread" [stack: 0x00007fa880d44000,0x00007fa880e44000] [id=126290]

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3135/files
  - new: https://git.openjdk.java.net/jdk/pull/3135/files/348edfc0..2381ba19

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=17
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=16-17

  Stats: 11 lines in 3 files changed: 11 ins; 0 del; 0 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