RFR: fixing jextract sample issues for jdk 22

[Athijegannathan Sundararajan]

* re-generated libjimage sources and manually adopted for library loding.
* avoid attempting to generate unsupported type constants ("long double")
* adjust shell scripts for different versions of native libraries
* allow Python home to be overridden by env. vars

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Commit messages:
 - * re-generated libjimage sources and manually adopted for library loading

Changes: https://git.openjdk.org/jextract/pull/174/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=174&range=00
  Stats: 888 lines in 20 files changed: 344 ins; 444 del; 100 mod
  Patch: https://git.openjdk.org/jextract/pull/174.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/174/head:pull/174

PR: https://git.openjdk.org/jextract/pull/174