[foreign-memaccess+abi] RFR: Rename max alignment constants for heap segments

[Jorn Vernee]

On Tue, 26 Sep 2023 14:39:42 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> The name of the max alignment constants in `HeapMemorySegmentImpl` is misleading: these constants use numeric values (e.g. `MAX_ALIGN_8`) but in reality the maximum supported alignment can vary depending on the platform (at least for segments wrapping `long[]` and `double[]` arrays).
> 
> This PR introduces a less confusing naming scheme, and a comment to call out the fact that some constants are platform-dependent.

Marked as reviewed by jvernee (Committer).

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PR Review: https://git.openjdk.org/panama-foreign/pull/897#pullrequestreview-1644652445