[master] RFR: 8305926: [Lilliput] Revert some ZGC changes

[Roman Kennke]

I'm cleaning up some stuff and found these changes in ZGC that we don't need anymore.

Testing:
 - [x] hotspot_gc
 - [x] tier1
 - [x] tier2

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

Commit messages:
 - 8305926: [Lilliput] Revert some ZGC changes

Changes: https://git.openjdk.org/lilliput/pull/84/files
 Webrev: https://webrevs.openjdk.org/?repo=lilliput&pr=84&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305926
  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/lilliput/pull/84.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/84/head:pull/84

PR: https://git.openjdk.org/lilliput/pull/84