Add report task that shows bytecode coverage

[Ezard]

Sometimes, it is very difficult to determine why a line is either partially covered or not covered at all

This is usually due to the fact that Kover reports on bytecode-level coverage, but then displays the coverage on top of the source code

With the ability to view which lines of bytecode are covered / not covered, it should be substantially easier to determine which paths through the code are actually untested

e.g. I'm currently trying to determine how the following coverage occurs:

when (response) { // fully covered
  is Success -> { // fully covered
    foo()         // fully covered
  }               // partially covered
  is Failure -> { // partially covered
    bar()         // fully covered
  }               // fully covered
}

It could be a bug with Kover, or it could be a weird path through the code that's been mapped strangely to the source code, or it could be something else - the ability to see bytecode coverage would allow this sort of thing to be diagnosed

[shanshin]

Relates #272

[shanshin]

This task will be taken into account when migrating to Kotlin Gradle Plugin.

In the future, it will be moved to the Kotlin task tracker, or closed if it loses relevance.