[jdk17] RFR: 8267952: async logging supports to dynamically change tags and decorators [v4]

[Xin Liu]

> This patch fixed intermittent crashes of gtest/AsyncLogGtest.java. The root cause 
> is that previous flush() can't guarantee flush all pending messages in AsyncLog
> buffer. This patch implements flush() using a synchronizaton token and waits for
> completion. This approach isn't MT-safe but it can serialize all flush() calls in
> a thread. 
> 
> Two concurrent tests are appended to cover the hazard cases.
> This patch also comments LogConfiguration::configure_output() MT-safety.

Xin Liu has updated the pull request incrementally with one additional commit since the last revision:

  Update comments part-2.

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Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/130/files
  - new: https://git.openjdk.java.net/jdk17/pull/130/files/3fc68f24..eb520356

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=130&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=130&range=02-03

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/130.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/130/head:pull/130

PR: https://git.openjdk.java.net/jdk17/pull/130