RFR: 8307532: Implement LM_LIGHTWEIGHT for Zero [v2]

[Julian Waters]

On Tue, 1 Oct 2024 13:42:35 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> The `LM_LIGHTWEIGHT` changes looks good to me.
> 
> This also enables `UseObjectMonitorTable`. I believe `BasicLock::object_monitor_cache()` must be modified as well. Assuming that both `ZERO` and a supported platform (e.g. `X86`) can and will be defined in the same build.
> 
> `ZERO` should return `nullptr` in `BasicLock::object_monitor_cache()` as well.

I might be missing something, but Zero cannot be combined with another VM variant in the configure step, so the risk of a CPU arch being defined at the same time as Zero cannot happen (The build system treats Zero a little strangely)

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PR Comment: https://git.openjdk.org/jdk/pull/21220#issuecomment-2386123951