[lworld] RFR: 8287040: [lworld][lw4] Remove abstract Object class support from HotSpot

[Frederic Parain]

Remove HotSpot support for an abstract Object class.

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Commit messages:
 - More test fixes
 - Fix tests
 - Remove unused local variable
 - Merge remote-tracking branch 'upstream/lworld' into reverting_abstract_object
 - Removing support for abstract Object class

Changes: https://git.openjdk.java.net/valhalla/pull/693/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=693&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287040
  Stats: 139 lines in 20 files changed: 0 ins; 118 del; 21 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/693.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/693/head:pull/693

PR: https://git.openjdk.java.net/valhalla/pull/693