Review servlet support for Weld 5

This issue is a follow-up for WELD-2696.

We need to review overall support for servlet in Weld 5.

This includes but might not be limited to:

• There are no running CI tests for servlets ATM, we need to re-enable them at least partially
  • See the CI settings, about 4 jobs are skipped
  • Actually, any in-container tests are disabled because there was neither viable EE server nor servlet at the time
• Jetty testing module has been disabled since EE 9/Weld 4 due to lacking adapter; issue is here
  • The issue is now resolved but that adapter is IMO for EE 9 version but we could test it
  • However, the upkeep of jetty assets has been historically way more difficult than Tomcat; not sure it is worth keeping at all
• Documentation mentions outdated Tomcat and Jetty versions and untested instructions
  • Servlets are no longer used much but we should keep at least some tests and some docs to have the code covered
  • Suggestion is to keep renew Tomcat testing and documentation (there is already an EE 10 Alpha version) and drop Jetty docs and jetty testing module. We can keep the integration on a best-effort basis
• If we make any breaking changes or drop support for some features, we should make it publicly known via announcement and possibly also contact relevant projects if they want to keep any testing (Jetty)