[foreign-memaccess+abi] RFR: 8292174: Add unaligned layouts to ValueLayout

[Per Minborg]

On Wed, 10 Aug 2022 13:03:45 GMT, Per Minborg <duke at openjdk.org> wrote:

> The layouts are placed in a special `Unaligned` class. This prevents the classes to be seen on the top level (for less cluttering) and allows lazy initialization of items that are likely not so much used.

`JAVA_BYTE` and `JAVA_BOOLEAN` are implicitly unaligned. We could either:

* provide `JAVA_BYTE_UNALIGNED` for symmetry which is identical to `JAVA_BYTE` (and the same for boolean).
* provide neither `JAVA_BYTE_UNALIGNED` nor `JAVA_BYTE_UNALIGNED`

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PR: https://git.openjdk.org/panama-foreign/pull/705