[REQ] Upgrade ktor to 3.4.0

[luisvt]

• Upgrade ktor to 3.4.0
• Upgrade kotlin to 2.3.0
• Upgrade gralde-wrapper to 9.2.1

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 WSL)
  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 solves a reported issue, reference it using GitHub's linking syntax (e.g., having "fixes #123" present in the PR description)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

@karismann @Zomzog @andrewemery @4brunu @yutaka0m @stefankoppier @e5l @dennisameling

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Summary by cubic

Upgraded Kotlin server templates to Ktor 3.4.0, Kotlin 2.3.0, and Gradle 9.2.1. Added the io.ktor Gradle plugin and updated samples; removed the Ktor BOM.

• Dependencies

  • Ktor 3.4.0 + io.ktor.plugin 3.4.0
  • Kotlin 2.3.0
  • Gradle wrapper 9.2.1

• Migration

  • Regenerate Kotlin server projects to pick up new versions.
  • For existing projects, apply io.ktor.plugin and remove the Ktor BOM; use Gradle ≥ 9.2.1.

^{Written for commit d847d87. Summary will update on new commits.}

[cubic-dev-ai]

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