RFR: 7903636: update jextract sample scripts for --source option removal [v4]

[Athijegannathan Sundararajan]

> * removing --source option in scripts
> * removing binary .class generating scripts (as normal scripts do compilation by javac anyway)
> * removing unnecessary --enable-preview option in run scripts.
> * updating gradle version to be the latest (8.5) so that we can use JDK 21 for gradle run itself.

Athijegannathan Sundararajan has updated the pull request incrementally with two additional commits since the last revision:

 - Merge pull request #5 from JornVernee/WinSamples
   
   Update windows sample scripts
 - update windows sample scripts

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Changes:
  - all: https://git.openjdk.org/jextract/pull/189/files
  - new: https://git.openjdk.org/jextract/pull/189/files/37f0d648..2eb19e05

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=189&range=03
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=189&range=02-03

  Stats: 45 lines in 16 files changed: 35 ins; 8 del; 2 mod
  Patch: https://git.openjdk.org/jextract/pull/189.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/189/head:pull/189

PR: https://git.openjdk.org/jextract/pull/189