RFR: 8301627: System.exit and Runtime.exit debug logging [v6]

[Roger Riggs]

> It can be difficult to find the cause of calls to `java.lang.System.exit(status)` and `Runtime.exit(status)` because the Java runtime exits.
> The status value and stack trace are logged using the System Logger named `java.lang.Runtime` with message level `System.Logger.Level.DEBUG`.

Roger Riggs 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 eight additional commits since the last revision:

 - Move test to the java/lang/RuntimeTests directory.
   Added implNote to System.exit.
   A few javadoc updates for review comments.
 - Merge branch 'master' into 8301627-log-system-exit
 - Improve implNote for Runtime.exit() with review suggestions.
 - Correct System.getLogger link
 - Add an @implNote to Runtime.exit to describe the java.lang.Runtime logging.
 - Added try/catch around lookup of logger so exceptions do not prevent System.exit.
   Added test case with console logger (when java.util.logging) not present.
   Removed @implNote tag its not appropriate in implementation javadoc.
   Still looking into when and where the log configuration should be described.
 - Locate the System logger before taking the shutdown lock
 - Add logging of calls to Runtime.exit to the system logger "java.lang.Runtime".

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12517/files
  - new: https://git.openjdk.org/jdk/pull/12517/files/a31645c1..3dc13135

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12517&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12517&range=04-05

  Stats: 48694 lines in 1053 files changed: 18511 ins; 14817 del; 15366 mod
  Patch: https://git.openjdk.org/jdk/pull/12517.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12517/head:pull/12517

PR: https://git.openjdk.org/jdk/pull/12517