RFR: JDK-8313804: JDWP support for -Djava.net.preferIPv6Addresses=system [v2]

[Liam Miller-Cushon]

> Please consider this fix for [JDK-8313804](https://bugs.openjdk.org/browse/JDK-8313804), which adds support to JDWP for `-Djava.net.preferIPv6Addresses=system`. Previously it only handled `-Djava.net.preferIPv6Addresses=true` and `-Djava.net.preferIPv6Addresses=false`.

Liam Miller-Cushon has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  JDK-8313804: JDWP support for -Djava.net.preferIPv6Addresses=system

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15796/files
  - new: https://git.openjdk.org/jdk/pull/15796/files/f74c2d4e..45178d06

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15796&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15796&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15796.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15796/head:pull/15796

PR: https://git.openjdk.org/jdk/pull/15796