RFR: 8257234 : Add gz option to SA jmap to write a gzipped heap dump [v20]

[Lin Zang]

> 8257234 : Add gz option to SA jmap to write a gzipped heap dump

Lin Zang has updated the pull request incrementally with two additional commits since the last revision:

 - fix indentation isue
 - fix help message issue and Use ByteBuffer for integer writing

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1712/files
  - new: https://git.openjdk.java.net/jdk/pull/1712/files/6fe0f79b..7c25d58c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1712&range=19
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1712&range=18-19

  Stats: 27 lines in 2 files changed: 11 ins; 7 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1712.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1712/head:pull/1712

PR: https://git.openjdk.java.net/jdk/pull/1712