Rebrand implicitConversion to autoConversion

[therealcisse]

Scala 3 improves implicit cnversion greatly by adding the Conversion type and other restrictions. And I think we can do even better by rebranding the entire idea of implicit conversions by renaming Conversion to AutoConversion and scala.language.implicitConversion to scala.language.autoConversion.

Implicits has a bad rap in Scala. Scala 3 has extracted many use cases of implicits into their own construct. I think conversions can also benefit from this effort.

Just throwing it out there.