Update Sinatra to version 4.0.0

[MiguelERuiz]

Description Sinatra should be upgraded to version 4.0.0 so that use the latest stable version of this gem. This change affects also the webserver Sinatra is going to use, since with version < 4 it's using Thin as webserver, meanwhile with version >= 4.0.0 Puma is the default webserver. So we must modify the Gemfile that is used by the install_gemsscript to update the version and also add the Puma gem since it's going to be necessary. Thin gem could be untouched although if it's not necessary anymore, it should be removed from the Gemfile.

Use case For version 7.0 of OpenNebula we want to update this gem and be up-to-date with the features Sinatra offers.

Interface Changes This change affects not only oneflow CLI as we cover on issue #6508 but also could affect other CLI like onegate so we must keep in mind this clients cannot vary their behavior by this change. Also we must review other servers like from oneprometheus that should not be affected by this change.

Additional Context

Progress Status

• [ ] Code committed
• [ ] Testing - QA
• [ ] Documentation (Release notes - resolved issues, compatibility, known issues)