RFR: 8229517: Support for optional asynchronous/buffered logging [v7]

[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:

  Support Jcmd pid VM.log disable
  
  This patch also supports to add a new output dynamically. If
  output_option specifies async=true, the new output will use
  asynchronous writing.
  
  Currently jcmd VM.log prohibts users from changing established
  output_options in runtime. users can disable them all and then
  recreate them with the new output_options.

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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/3d74a32b..2bd104ff

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=06
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=05-06

  Stats: 13 lines in 2 files changed: 11 ins; 0 del; 2 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