[foreign-jextract] [Rev 03] RFR: 8239809: Need API to access attributes

[Henry Jen]

> Add API to allow associate attributes with Declaration.
> 
> An attribute can have multiple values, thus a list of ConstantDesc.
> 
> The test case is based on [JDK-8223105](https://bugs.openjdk.java.net/browse/JDK-8223105), Windows test is simply parsing at this point, need to add validation as the header is implemented differently. 
> 
> We may want to add a more generic test case with some standard attributes.

The pull request has been updated with 1 additional commit.

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

Added commits:
 - d5cb51dc: Change API to withAttribute(String, Constable...)

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/33/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/33/files/49b308e4..d5cb51dc

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/33/webrev.03
 - incr: https://webrevs.openjdk.java.net/panama-foreign/33/webrev.02-03

  Stats: 83 lines in 4 files changed: 78 ins; 1 del; 4 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/33.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/33/head:pull/33

PR: https://git.openjdk.java.net/panama-foreign/pull/33