Fix #7352

Changes to the codegen/template:

• Update to Vert.x 4
• Removed rx java: although it's used by some people in Vert.x community, it's an opinionated choice and rx users (which usually are not beginners) can easily add it without much pain. On the contrary, removing it for a beginner it's non trivial.
• Removed some useless classes on the template that are already provided by Vert.x itself (like ApiException, which maps to HttpStatusException)

Signed-off-by: Francesco Guardiani [email protected]

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.
• If contributing template-only or documentation-only changes which will change sample output, build the project beforehand.
• Run the shell script ./bin/generate-samples.shto update all Petstore samples related to your fix. 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*. For Windows users, please run the script in Git BASH.
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Additional context

So the generator works perfectly, generates compiling code and runs it. But, if you run the generated sample, the application crash because of a bug i've found while developing this generator 😄 I fixed it and, with the new version bump, it should work fine vert-x3/vertx-web#1696