RFR: 7903680: Dependency checker doesn't handle function pointers and nested types

[Maurizio Cimadamore]

This patch fixes few issues in the new dependency checker. As usual, the new visitor was skipping a bunch of cases, which resulted in errors not being reported:
* if a variable, function parameter/return, typedef had function pointer type, we did not propagate the visit to the function type
* if there's nested declarations in a typedef, function, variable, we also did not propagate.

I added the required propagation, and a new test which checks that errors are generated in these cornery situations.

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Commit messages:
 - Initial push

Changes: https://git.openjdk.org/jextract/pull/224/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=224&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903680
  Stats: 154 lines in 3 files changed: 145 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jextract/pull/224.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/224/head:pull/224

PR: https://git.openjdk.org/jextract/pull/224