[foreign-jextract] RFR: 8247439: NativeAllocationScope should have a way to register existing segments onto it

[Athijegannathan Sundararajan]

Sync'ed with changes in 'foreign-abi'

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Commit messages:
 - 8247486: CScope class should be removed. NativeScope should be used instead.

Changes: https://git.openjdk.java.net/panama-foreign/pull/201/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/201/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8247439
  Stats: 252 lines in 14 files changed: 15 ins; 61 del; 176 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/201.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/201/head:pull/201

PR: https://git.openjdk.java.net/panama-foreign/pull/201