RFR: Tweak jextract to reflect changes to `MemorySegment::ofAddress`

[Maurizio Cimadamore]

This patch brings jextract in sync with the API changes in https://git.openjdk.org/panama-foreign/pull/797.

The changes are mostly trivial and, luckily, jextract bindings already shield developers from having to call `MemorySegment::ofAddress` manually, so not a lot of test changes were required.

I've also updated the samples (but I could not test them as my environment is not setup to do that). We will fix up samples issues later (if needed).

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Commit messages:
 - Fix samples
 - Merge branch 'panama' into reinterpret
 - Initial push

Changes: https://git.openjdk.org/jextract/pull/105/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=105&range=00
  Stats: 44 lines in 20 files changed: 2 ins; 1 del; 41 mod
  Patch: https://git.openjdk.org/jextract/pull/105.diff
  Fetch: git fetch https://git.openjdk.org/jextract pull/105/head:pull/105

PR: https://git.openjdk.org/jextract/pull/105