RFR: fixing jextract sample issues for jdk 22 [v4]

[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

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last revision:

  avoiding long double. using __int128 instead (Windows)

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Changes:
  - all: https://git.openjdk.org/jextract/pull/174/files
  - new: https://git.openjdk.org/jextract/pull/174/files/c45d5385..27813e6a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=174&range=03
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=174&range=02-03

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 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