[foreign-abi] RFR: 8252872: NativeScope should take Addressable instead of MemoryAddress

[Maurizio Cimadamore]

The routines for creating a memory segment initialized to a given initial MemoryAddress value should be updated to
allow clients to pass any Addressable.

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Commit messages:
 - Tweak NativeScope to accept Addressable instead of MemoryAddress

Changes: https://git.openjdk.java.net/panama-foreign/pull/311/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=311&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252872
  Stats: 14 lines in 1 file changed: 1 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/311.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/311/head:pull/311

PR: https://git.openjdk.java.net/panama-foreign/pull/311