[foreign-jextract] RFR: 8263018: Improve API for lifecycle of native resources [v2]

[Maurizio Cimadamore]

> This contains the jextract changes required to support the new changes to the foreign memory access API.
> 
> The main change is that now NativeScope is co-generated by jextract (although, moving forward, I'm not sure how much value it adds, but that's for another day).
> 
> I had to fix the extracted libclang in few places (probably better to re-generate this code once this is pushed).
> 
> Tests needed changes to fix imports so that they pick up the generated NativeScope class.

Maurizio Cimadamore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 98 commits:

 - Merge branch 'foreign-jextract' into jextract+resourceScope
 - Merge branch 'foreign-memaccess+abi' into jextract+resourceScope
 - Merge branch 'foreign-jextract' into jextract+resourceScope
 - Add overloads accepting ResourceScope parameter
 - Merge branch 'resourceScope' into jextract+resourceScope
 - Add ResourceScope overloads in CLinker
   Rewrite StdLib test not to use NativeScope
   Tweak names of allocator factories
   Fix javadoc
 - All tests pass
   * Fix upcall overload taking NativeScope
   * Generate NativeScope in output package
   * Add overload for functions returning a struct so than a NativeScope can be passed
   * Removed some now unused features from RuntimeHelper (ti make scope non-transferrable)
   * Fixup vararg invoker to deal with allocator parameters
   * Fixup tests to (a) depend on the generated NativeScope and (b) not to use TWR with segments directly
   Notes:
   * the internal libclang probably needs to be re-generated
 - Merge branch 'resourceScope' into jextract+resourceScope
 - Fix javadoc of SegmentAllocator
 - Address rest of review comments from Paul
 - ... and 88 more: https://git.openjdk.java.net/panama-foreign/compare/4e696684...6316ddca

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Changes: https://git.openjdk.java.net/panama-foreign/pull/474/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=474&range=01
  Stats: 520 lines in 35 files changed: 279 ins; 99 del; 142 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/474.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/474/head:pull/474

PR: https://git.openjdk.java.net/panama-foreign/pull/474