[foreign-jextract] RFR: 8263018: Improve API for lifecycle of native resources [v3]

[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 incrementally with one additional commit since the last revision:

  Addressed review comments
  Add a debug allocator to the internal libclang which can be used to monitor/review allocator usage from libclang function

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/474/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/474/files/6316ddca..65f7de7b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=474&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=474&range=01-02

  Stats: 61 lines in 7 files changed: 33 ins; 0 del; 28 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