[foreign-memaccess+abi] RFR: Simplify ValueLayouts [v2]

[Maurizio Cimadamore]

On Thu, 16 Feb 2023 10:26:20 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposes a more shortened and simplified scheme when implementing value layouts. 
>> 
>> This provides a significant reduction of the code size. A new threeary duplicator is introduced. In the solution below, I sugest using a function (`ValueLayoutDuplicator<V>`) which reduces code but arguably makes it a bit more complicated. Another alternative would be to simply mandate a corresponding abstract method and Implement an explicit delegator to the constructor for each type. 
>> 
>> Let me know your thoughts around how to balance this.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rework duplicator

Looks very nice - thanks!

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Marked as reviewed by mcimadamore (Committer).

PR: https://git.openjdk.org/panama-foreign/pull/798