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

[Roman Kennke]

On Fri, 16 Jun 2023 15:22:00 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> 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`
>  - [x] Linux x86_64 tier1, out of box
>  - [ ] Linux x86_64 tier1, `-XX:+UnlockExperimentalVMOptions -XX:+UseCompactObjectHeaders`
>  - [ ] Linux x86_64 tier1, `-XX:+UnlockExperimentalVMOptions -XX:-UseCompactObjectHeaders`

Looks good and makes sense. Thanks!

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Marked as reviewed by rkennke (Lead).

PR Review: https://git.openjdk.org/lilliput/pull/99#pullrequestreview-1483763317