Future task suggestions

• [Java 21] Plan roadmap for upgrade to Java 21 (to be released end of September 2023)
• [Launcher] Support multiple java versions
• [CI/Tooling] Elaborate workspace repo in #4035 (roadmap)
• [CI/Tooling] Elaborate CI setup improvements in #5136 (gap analysis, roadmap)
  • Fix compile errors
  • see BenjaminAmos@d252362
• investigate #5056
• investigate issues related to ctrl / shift / crouching / running / movement in general
  (#5224 #2565 #1075 #4300 #2833 #4993)

task suggestions:

• remove core registry in favor of context (e.g. #4508)
• continue subsystem extraction (see #4304)
• game initialization phases (see #2774 and various other engine issues)
• upgrade protobuf gradle plugin 0.8.16 -> 0.9.x (https://github.com/google/protobuf-gradle-plugin/releases) and compiler 3.17.0 -> 3.17.3