RFR: 7903663: update jextract sample scripts for library loading and varargs handling changes

[Athijegannathan Sundararajan]

* all samples updated to use -l <name> or -l :<path> options. 
* No -Djava.library.path settings in run.sh.
* libjimage avoid pre-extracted checked-in sources.

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Commit messages:
 - 7903663: update jextract sample scripts for library loading and varargs handling changes

Changes: https://git.openjdk.org/jextract/pull/210/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=210&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903663
  Stats: 902 lines in 40 files changed: 25 ins; 841 del; 36 mod
  Patch: https://git.openjdk.org/jextract/pull/210.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/210/head:pull/210

PR: https://git.openjdk.org/jextract/pull/210