RFR: 8296420: javac has long lines in its command-line help

[Archie L. Cobbs]

The issue states that the output of `javac --help` and `javac --help-extra` should not overflow 80 columns.

This patch updates `javac.properties` to add newlines, etc. to address this issue, and adds a regression test.

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Commit messages:
 - Restrict javac command line help output to 80 columns.

Changes: https://git.openjdk.org/jdk/pull/13329/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13329&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296420
  Stats: 126 lines in 2 files changed: 105 ins; 0 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/13329.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13329/head:pull/13329

PR: https://git.openjdk.org/jdk/pull/13329