[foreign-memaccess+abi] RFR: API refresh - part two [v3]

[Maurizio Cimadamore]

> After playing a bit more with the new API changes, I realized there were issues with some of the solutions proposed in [1].
> I will add more details in a separate comment, to keep the header of this PR compact.
> 
> [1] - https://git.openjdk.java.net/panama-foreign/pull/576

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

  Fix code snippet in SegmentAllocator::nativeAllocator

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/591/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/591/files/acfdf4d2..97e6b59e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=591&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=591&range=01-02

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/591.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/591/head:pull/591

PR: https://git.openjdk.java.net/panama-foreign/pull/591