#25513 Prepare 7.28.0-SNAPSHOT

PR checklist

• Read the contribution guidelines.
• 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.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

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Summary by cubic

Prepares the 7.28.0 development cycle by bumping all module versions from 7.27.0 to 7.28.0-SNAPSHOT and reverting the 7.27.0 release commit. The README now lists 7.28.0 as the upcoming minor release and 7.27.0 as the latest stable release, and generated samples have been regenerated to match.