RFR: 8282191: Implementation of Foreign Function & Memory API (Preview) [v34]

[Maurizio Cimadamore]

> This PR contains the API and implementation changes for JEP-424 [1]. A more detailed description of such changes, to avoid repetitions during the review process, is included as a separate comment.
> 
> [1] - https://openjdk.java.net/jeps/424

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Downcall and upcall tests use wrong layout which is missing some trailing padding

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7888/files
  - new: https://git.openjdk.java.net/jdk/pull/7888/files/5866bbb5..945317ec

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7888&range=33
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7888&range=32-33

  Stats: 9 lines in 2 files changed: 7 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7888.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7888/head:pull/7888

PR: https://git.openjdk.java.net/jdk/pull/7888