ZIO Test: Add new spec type

To provide a more “flat” style and without any commas, it would be nice to define a mutable spec, supporting the following syntax:

object MySpec extends MutableRunnableSpec {
  suite("foo") {
    testM("name") {
    } @@ ignore

    test("name 2") {
      suite("another suite") {
      }
    }
  }
}

This would be accomplished by defining suite and test and testM methods directly inside MutableRunnableSpec, which would mutably append to a data structure, which would be materialized when the def spec of the parent runnable spec is called.

In order to support annotations, the test and suite methods would have to return some object with @@ side-effect method, which modifies in-place the last definition by applying the test aspect.

The goal would be to preserve the existing ZIO Test syntax and feature set almost exactly, while at the same time getting away from the “comma” syntax which many find annoying.

[fokot]

I will take this

[hmemcpy]

Also I think this issue can be closed?