[foreign-abi] RFR: Merge foreign-memaccess

[Maurizio Cimadamore]

This merge fixes both conflicts coming from:

https://git.openjdk.java.net/panama-foreign/pull/88

and

https://git.openjdk.java.net/panama-foreign/pull/84

Some downstream work in foreign-jextract will likely be required.

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

Commit messages:
 - * Fix whitespaces
 - Merge with changes to add API point to get raw long address value
 - JDK-8242048: Add API point to get raw long value out of a MemoryAddress
 - Merge address combinator changes
 - JDK-8242046: Add a predicate to determine if MemoryLayout is a padding layout
 - JDK-8242011: Add support for memory address combinator

Changes: https://git.openjdk.java.net/panama-foreign/pull/89/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/89/webrev.00
  Stats: 3092 lines in 39 files changed: 1617 ins; 1272 del; 203 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/89.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/89/head:pull/89

PR: https://git.openjdk.java.net/panama-foreign/pull/89