RFR: 6909: Upgrade to Eclipse 2020-09 [v12]

[Marcus Hirt]

> Adds the Eclipse 2020-09 platform, upgrades 2020-09 and 2020-06 to use the 2020-06 babel bundles, and sets 2020-09 to
> be the default.

Marcus Hirt has updated the pull request incrementally with one additional commit since the last revision:

  Fixing some connection leaks in tests and adding debuggability features

-------------

Changes:
  - all: https://git.openjdk.java.net/jmc/pull/111/files
  - new: https://git.openjdk.java.net/jmc/pull/111/files/6e5a56c3..88f6e093

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=111&range=11
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=111&range=10-11

  Stats: 381 lines in 3 files changed: 194 ins; 173 del; 14 mod
  Patch: https://git.openjdk.java.net/jmc/pull/111.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/111/head:pull/111

PR: https://git.openjdk.java.net/jmc/pull/111