RFR: Backport: 7903449: Jextract generates structs that cannot be compiled

[Maurizio Cimadamore]

On Sun, 9 Apr 2023 00:32:09 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Backport https://github.com/openjdk/jextract/pull/117 to the master branch.
> 
> Patch applied relatively cleanly. I had to change some reference from `Arena` to `SegmentScope` in the generated code, and there was a reference to `MS::reinterpret` that was changed back to `ofAddress`.
> 
> Additional changes needed:
> - AddressLayout -> ValueLayout.ofAddress
> - AddressLayout::withTargetLayout -> AddressLayout::asUnbounded
> - reimplement ValueLayout::withoutName as helper function

Looks good

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Marked as reviewed by mcimadamore (Committer).

PR Review: https://git.openjdk.org/jextract/pull/118#pullrequestreview-1385268437