Simplify & cleanup some test task definitions (scala#6798)

Simplify test task definitions

If you're not interested in the task results, don't ask for them. That
way you don't have to work around discarding them too!

Remove testRest, which had been added when we were running 
into time limits,  but we no longer are.

build.sbt

@@ -770,6 +770,12 @@ lazy val scalaDist = Project("scala-dist", file(".") / "target" / "scala-dist-di
   )
   .dependsOn(library, reflect, compiler, scalap)
 
+def partestOnly(in: String): Def.Initialize[Task[Unit]] =
+  (testOnly in IntegrationTest in testP).toTask(" -- " + in)
+
+def partestDesc(in: String): Def.Initialize[Task[(Result[Unit], String)]] =
+  partestOnly(in).result map (_ -> s"partest $in")
+
 lazy val root: Project = (project in file("."))
   .settings(disableDocs)
   .settings(disablePublishing)
@@ -799,35 +805,20 @@ lazy val root: Project = (project in file("."))
       state
     },
 
-    testRun := { val v = (testOnly in IntegrationTest in testP).toTask(" -- run").result.value },
-
-    testPosPres := { val v = (testOnly in IntegrationTest in testP).toTask(" -- pos presentation").result.value },
-
-    testRest := {
-      val v = ScriptCommands.sequence[Result[Unit]](List(
-          (mimaReportBinaryIssues in library).result,
-          (mimaReportBinaryIssues in reflect).result,
-          (Keys.test in Test in junit).result,
-          (Keys.test in Test in scalacheck).result,
-          (testOnly in IntegrationTest in testP).toTask(" -- neg jvm").result,
-          (testOnly in IntegrationTest in testP).toTask(" -- res scalap specialized").result,
-          (testOnly in IntegrationTest in testP).toTask(" -- instrumented").result,
-          (testOnly in IntegrationTest in testP).toTask(" -- --srcpath scaladoc").result,
-          (Keys.test in Test in osgiTestFelix).result,
-          (Keys.test in Test in osgiTestEclipse).result)).value
-    },
+    testRun := partestOnly("run").value,
+    testPosPres := partestOnly("pos presentation").value,
 
-    // all of testRun, testPosPres, testRest and more
+    // all of testRun, testPosPres and more
     testAll := {
       val results = ScriptCommands.sequence[(Result[Unit], String)](List(
         (Keys.test in Test in junit).result map (_ -> "junit/test"),
         (Keys.test in Test in scalacheck).result map (_ -> "scalacheck/test"),
-        (testOnly in IntegrationTest in testP).toTask(" -- run").result map (_ -> "partest run"),
-        (testOnly in IntegrationTest in testP).toTask(" -- pos neg jvm").result map (_ -> "partest pos neg jvm"),
-        (testOnly in IntegrationTest in testP).toTask(" -- res scalap specialized").result map (_ -> "partest res scalap specialized"),
-        (testOnly in IntegrationTest in testP).toTask(" -- instrumented presentation").result map (_ -> "partest instrumented presentation"),
-        (testOnly in IntegrationTest in testP).toTask(" -- --srcpath scaladoc").result map (_ -> "partest --srcpath scaladoc"),
-        (testOnly in IntegrationTest in testP).toTask(" -- -Dpartest.scalac_opts=-Ymacro-annotations --srcpath macro-annot").result map (_ -> "partest --srcpath macro-annot"),
+        partestDesc("run"),
+        partestDesc("pos neg jvm"),
+        partestDesc("res scalap specialized"),
+        partestDesc("instrumented presentation"),
+        partestDesc("--srcpath scaladoc"),
+        partestDesc("-Dpartest.scalac_opts=-Ymacro-annotations --srcpath macro-annot"),
         (Keys.test in Test in osgiTestFelix).result map (_ -> "osgiTestFelix/test"),
         (Keys.test in Test in osgiTestEclipse).result map (_ -> "osgiTestEclipse/test"),
         (mimaReportBinaryIssues in library).result map (_ -> "library/mimaReportBinaryIssues"),
@@ -954,7 +945,6 @@ lazy val testAll = taskKey[Unit]("Run all test tasks sequentially")
 
 lazy val testRun = taskKey[Unit]("Run compute intensive test tasks sequentially")
 lazy val testPosPres = taskKey[Unit]("Run compilation test (pos + presentation) sequentially")
-lazy val testRest = taskKey[Unit]("Run the remaining test tasks sequentially")
 
 // Defining these settings is somewhat redundant as we also redefine settings that depend on them.
 // However, IntelliJ's project import works better when these are set correctly.