Add gradle wrapper v8.1.1 to kotlin-spring

[DavidGrath]

Added gradle wrapper files to generated output for kotlin-spring and also the cloud variant

Fix #20321 by @takkiraz

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

[wing328]

Just triggered all tests via #20359

Let's see how that goes

UPDATE: tests passed

[wing328]

Did a test and the result looks good:

$ ./gradlew build
Downloading https://services.gradle.org/distributions/gradle-8.1.1-bin.zip
...........10%............20%............30%............40%............50%............60%............70%............80%...........90%............100%

Welcome to Gradle 8.1.1!

Here are the highlights of this release:
 - Stable configuration cache
 - Experimental Kotlin DSL assignment syntax
 - Building with Java 20

For more details see https://docs.gradle.org/8.1.1/release-notes.html

Starting a Gradle Daemon (subsequent builds will be faster)

BUILD SUCCESSFUL in 5m 46s
6 actionable tasks: 6 executed

[DavidGrath]

@wing328 Thank you!