[master] RFR: 8310214: [Lilliput] Disable compact headers by default [v2]

[Aleksey Shipilev]

> This would match the PRs that we eventually upstream, and would capture the tests that are failing/misbehaving without compact headers better. This would require enabling `UCOH` for testing explicitly. I took additional care to allow `@flagless` tests with `-XX:+UnlockExperimentalVMOptions -XX:+UseCompactObjectHeaders`.
> 
> Additional testing:
>  - [x] Checked sample `@flagless` tests run with/without `UCOH`
>  - [ ] Linux x86_64 tier1, out of box
>  - [ ] Linux x86_64 tier1, `-XX:+UnlockExperimentalVMOptions -XX:+UseCompactObjectHeaders`
>  - [ ] Linux x86_64 tier1, `-XX:+UnlockExperimentalVMOptions -XX:-UseCompactObjectHeaders`

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Fix CompressedClassPointerEncoding test

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

Changes:
  - all: https://git.openjdk.org/lilliput/pull/99/files
  - new: https://git.openjdk.org/lilliput/pull/99/files/a50df26c..94a97a34

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput&pr=99&range=01
 - incr: https://webrevs.openjdk.org/?repo=lilliput&pr=99&range=00-01

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/lilliput/pull/99.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/99/head:pull/99

PR: https://git.openjdk.org/lilliput/pull/99