End poem, splashes and credits are plain text

The end poem, splashes and credits aren't translated and aren't available on Crowdin. There is already a similar report (MC-46341), but it doesn't address this text.

They also still use the § symbol for formatting, this should no longer be used and be changed to the json text component system.

Note: It also uses PLAYERNAME as player name place holder and [C] to align text centered. It would be better if this was solved then with text components as well.