RFR: 6847: Upgrading to the Eclipse 2020-06 platform

[Marcus Hirt]

Note that this one should probably go in after we get JMC-6838 in. That said, we can review it and get it ready for
show-time.

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Commit messages:
 - 6847: Upgrading to the Eclipse 2020-06 platform

Changes: https://git.openjdk.java.net/jmc/pull/85/files
 Webrev: https://webrevs.openjdk.java.net/jmc/85/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6847
  Stats: 157 lines in 5 files changed: 154 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/85.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/85/head:pull/85

PR: https://git.openjdk.java.net/jmc/pull/85