[foreign-jextract] [Rev 01] 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.

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Added commits:
 - 170b9ba8: Remove attributes support from public factory methods

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/33/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/33/files/c26d157f..170b9ba8

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/33/webrev.01
 - incr: https://webrevs.openjdk.java.net/panama-foreign/33/webrev.00-01

  Stats: 56 lines in 4 files changed: 22 ins; 13 del; 21 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