Rename ScoreHolderArgumentType.getScoreboardScoreHolders

[Cypher121]

The difference between getScoreHolders and this is that this method defaults to getting all known players instead of throwing an exception.

Mojmap's getNamesWithDefaultWildcard is closer to the truth, though still not ideal: not obvious that default wildcard here means "default to selecting all if no players found"

[monkero]

Maybe something like getAnyPlayer, since it gets anything.