RFR: 8335912: Add an operation mode to the jar command when extracting to not overwriting existing files

[Henry Jen]

This PR support a -k, --keep options like tar that allows jar to avoid override existing files.

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Commit messages:
 - Add simple test
 - Support legacy mode
 - 8335912: Add an operation mode to the jar command when extracting to not overwriting existing files

Changes: https://git.openjdk.org/jdk/pull/21141/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21141&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335912
  Stats: 275 lines in 4 files changed: 274 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21141.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21141/head:pull/21141

PR: https://git.openjdk.org/jdk/pull/21141