RFR: 8317819: Scope should reflect lifetime of underying resource (mainline) [v2]

[Maurizio Cimadamore]

> This PR is based on a port of: openjdk/panama-foreign#898
> 
> Some additional changes are contained in this PR:
> 
> * instead of using a different "always alive" scope for zero-length memory segments, we now use the global scope
> * the javadoc for `MemorySegment::ofArray`, `MemorySegment::ofBuffer` and `SymbolLookup::loaderLookup` is tweaked to say that the scope associated to the returned segments is an automatic scope
> * the javadoc for `MemorySegment.Scope` defines the concepts of global and automatic scope, which are then referenced in the `Arena` javadoc.

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

  Add test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16183/files
  - new: https://git.openjdk.org/jdk/pull/16183/files/c4631037..a9de77cd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16183&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16183&range=00-01

  Stats: 122 lines in 1 file changed: 122 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16183.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16183/head:pull/16183

PR: https://git.openjdk.org/jdk/pull/16183