RFR: 8257184: Upstream 8252504: Add a method to MemoryLayout which returns a offset-computing method handle [v2]

[Jorn Vernee]

> This upstreams the patch from: https://github.com/openjdk/panama-foreign/pull/396
> 
> There were only some minor merge conflicts due to imports and some tests being replaced by java/foreign/TestNulls. All tests still pass, no other changes were needed.
> 
> CSR: https://bugs.openjdk.java.net/browse/JDK-8257187

Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments:
  - remove explicit @throws NPE tags
  - add example to class doc

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1468/files
  - new: https://git.openjdk.java.net/jdk/pull/1468/files/1557fe64..4b632628

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1468&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1468&range=00-01

  Stats: 17 lines in 1 file changed: 13 ins; 4 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1468.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1468/head:pull/1468

PR: https://git.openjdk.java.net/jdk/pull/1468