RFR: 8295044: Implementation of Foreign Function and Memory API (Second Preview) [v20]

[Maurizio Cimadamore]

> This PR contains the API and implementation changes for JEP-434 [1]. A more detailed description of such changes, to avoid repetitions during the review process, is included as a separate comment.
> 
> [1] - https://openjdk.org/jeps/434

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

  Rename MemorySession -> SegmentScope
  Improve javadoc of SegmentScope/Arena
  Address review comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10872/files
  - new: https://git.openjdk.org/jdk/pull/10872/files/20ee6e8d..5ae5864a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10872&range=19
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10872&range=18-19

  Stats: 1298 lines in 125 files changed: 174 ins; 177 del; 947 mod
  Patch: https://git.openjdk.org/jdk/pull/10872.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10872/head:pull/10872

PR: https://git.openjdk.org/jdk/pull/10872