Reduce or eliminate usage of non-local returns

[raquo]

Semi-related to #519 by the goal of improving Scala.js debugging experience.

scala-java-time makes liberal use of non-local returns, e.g.:

      for (trans <- transArray) {
        info = findOffsetInfo(dt, trans)
        if (info.isLeft || (info == Right(trans.getOffsetBefore)))
          return info
      }

On the JS platform, Scala.js tries to compile non-local returns to native return and break, but this is not always possible, so they are sometimes compiled to use the NonLocalReturnControl exception.

This presents a problem for debugging Scala.js code in the browser, because you often want to use the Break on caught exceptions debugger option (e.g. to catch the origin of the exception in effect systems / observable graphs), but scala-java-time's NonLocalReturnControl exceptions trigger the debugger just as well in that case, and when working with date-heavy code, skipping through all those exceptions becomes unfeasible. I hoped that having fixed sourcemaps, I would be able to use the browser's "don't break here" option, but it does not seem to work, not sure why.

Also, nonlocal returns as a language feature are already throwing compiler deprecation warnings in Scala 3, so we do need a long term solution for that anyway.

With all that in mind, would you entertain a PR replacing nonlocal returns with equivalent constructs, e.g. while loops, else branches, etc.? There's a lot of such returns, I don't know if I can replace all of them, but I could at least get started on that.

[cquiroz]

Seems a good idea, feel free to send a PR