gradlew(.bat) should pass --parallel flag [LUCENE-9181]

Followup to #10219.

For example I have 2 real cores (4 apparent cpus, hyperthreads).
With #10219 change the build will work the first time, but it will only use one builder and take an eternity.

Instead if these wrappers passed --parallel then the first build would use 4 builders (built in gradle default).

Subsequent builds for me would only use 2, we still pass --parallel but now our gradle.properties tells it to only use 2

would give a better first experience (fans spin a bit higher for that first build, but better than slow as hell?)

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Migrated from [LUCENE-9181](https://issues.apache.org/jira/browse/LUCENE-9181) by Robert Muir (@rmuir)

Start with the gradlew and gradlew.bat wrapper files referenced in the issue, and review follow-up issue #10219 for the surrounding build change. Confirm that both wrappers pass --parallel while preserving the gradle.properties limit for subsequent builds, then run the wrapper build to verify the first build uses parallel workers.

Written by the indexing model from the issue text.