[foreign-abi] [Rev 03] RFR: 8241504: Expose MemoryLayout annotations/attributes in the public API

[Jorn Vernee]

> Hi,
> 
> This PR exposed MemoryLayout attributes in the public API.
> 
> A summary of the changes:
> - Renamed annotation -> attribute everywhere to avoid confusion with Java language annotations
> - Made sure that annotations were being serialized as part of a MemoryLayout's ConstantDesc, as well as the alignment
>   which was previously left out. (The latter also meant changing PaddingLayout::hasNaturalAlignment to always return
>   `true`, so serializing alignment is skipped for padding). Removed special casing for the abiType attribute. This can
>   now instead be handled through the generic attribute mechanism.
> 
> Thanks,
> Jorn

Jorn Vernee has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch 'Attributes' of https://github.com/JornVernee/panama-foreign into Attributes
 - Remove ML::attribute(String, Class) helper method.

-------------

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/64/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/64/files/380a1b04..d3baa351

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/64/webrev.03
 - incr: https://webrevs.openjdk.java.net/panama-foreign/64/webrev.02-03

  Stats: 32 lines in 5 files changed: 7 ins; 20 del; 5 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/64.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/64/head:pull/64

PR: https://git.openjdk.java.net/panama-foreign/pull/64