RFR: 8273682: Upgrade Jline to 3.20.0

[Jan Lahoda]

I'd like to upgrade the internal JLine to 3.20.0, to support the rxvt terminal (see JDK-8270943), and to generally use a newer version of the library. This patch is basically a application of relevant parts of the diff between JLine 3.14.0 and 3.20.0, with merge fixes as needed.

Thanks!

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Commit messages:
 - Removing trailing whitespace.
 - Fixing tests.
 - Fixing Windows build.
 - Upgrading JLine to 3.20.0

Changes: https://git.openjdk.java.net/jdk/pull/5655/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5655&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273682
  Stats: 2667 lines in 47 files changed: 1830 ins; 473 del; 364 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5655.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5655/head:pull/5655

PR: https://git.openjdk.java.net/jdk/pull/5655