RFR: 7903525: JOL: heapdumpstats usability improvements

[Aleksey Shipilev]

We need to be able to sort by column, have better descriptions, etc. Additionally, it does not have to read the large arrays for just the stats.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jol/pull/48/files
 Webrev: https://webrevs.openjdk.org/?repo=jol&pr=48&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903525
  Stats: 102 lines in 5 files changed: 45 ins; 16 del; 41 mod
  Patch: https://git.openjdk.org/jol/pull/48.diff
  Fetch: git fetch https://git.openjdk.org/jol.git pull/48/head:pull/48

PR: https://git.openjdk.org/jol/pull/48