Lift 5: Support Scala 3 Exclusively

[dpp]

https://groups.google.com/g/liftweb/c/sG2HWm4I3g0/m/fP7Al5amCAAJ?utm_medium=email&utm_source=footer

Per Lorenzo, migrate the Lift codebase to coding/run in Scala 3

[farmdawgnation]

Updated to title to reflect current conversation.