Implement error method with an additinal error message and cause

[tanishiking]

The first step to tackle this issue: scalameta/scalafmt#1628

Without this implementation, the reporter ends up discarding the error information of the cause of default void error(Path file, String message, Throwable e).
For example, the original cause of CorruptedClassPath is discarded, and currently, we have no clue to tackle this kind of problem: scalameta/scalafmt#1628

Because

• The default implementation of default void error(Path file, String message, Throwable e) is something like this: wrapping the additional message with RuntimeException and put the original exception to the cause of the RuntimeException
  • https://github.com/scalameta/scalafmt/blob/dee798a99e16dcf32fea37cdc05d694b76647ada/scalafmt-interfaces/src/main/java/org/scalafmt/interfaces/ScalafmtReporter.java#L29-L39
• SbtScalafmtReporter doesn't show the information of the cause if there's a message:

  • sbt-scalafmt/plugin/src/main/scala/org/scalafmt/sbt/ScalafmtSbtReporter.scala

    Lines 19 to 25 in ed2efe2

    	override def error(file: Path, e: Throwable): Unit = {
    	if (e.getMessage != null) {
    	error(file, e.getMessage)
    	} else {
    	throw new FailedToFormat(file.toString, e)
    	}
    	}

---

So this PR enables SbtScalafmtReporter to show the original error message passed via the third argument of default void error(Path file, String message, Throwable e).

[tanishiking]

Thank you for reviewing! I'm gonna cut a new release today.