RFR: Merge master

[Jorn Vernee]

Merge master branch into the jdk21 branch, to archive it before merging jdk22 into master

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Commit messages:
 - Merge branch 'master' into jdk21
 - Update jextract 21 with latest fixes
 - Merge branch 'jdk21'
 - Backport: 7903449: Jextract generates structs that cannot be compiled
 - Merge
 - Bring jdk20 branch in sync with panama branch
 - 7903435: TestDocComments fails on Windows
 - 7903436: Changes needed for jdk20-based makefile build
 - Fix code sample in README
 - Update GHA to jdk20
 - ... and 3 more: https://git.openjdk.org/jextract/compare/f8d22977...dc3de45a

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/jextract/pull/206/files
  Stats: 291 lines in 11 files changed: 218 ins; 48 del; 25 mod
  Patch: https://git.openjdk.org/jextract/pull/206.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/206/head:pull/206

PR: https://git.openjdk.org/jextract/pull/206