Get rid of KTUsefulTestCase, improve stability of the tests

plugins/scripting/scripting-compiler/build.gradle.kts

@@ -7,8 +7,6 @@ plugins {
 }
 
 dependencies {
-    testRuntimeOnly(intellijDep()) // Should come before compiler, because of "progarded" stuff needed for tests
-
     compileOnly(project(":compiler:frontend"))
     compileOnly(project(":compiler:frontend.java"))
     compileOnly(project(":compiler:psi"))
@@ -35,6 +33,7 @@ dependencies {
     testCompile(commonDep("junit:junit"))
 
     testImplementation(intellijCoreDep()) { includeJars("intellij-core") }
+    testRuntimeOnly(intellijDep()) { includeJars("jps-model") }
 }
 
 sourceSets {
@@ -58,7 +57,7 @@ javadocJar()
 
 testsJar()
 
-projectTest {
+projectTest(parallel = true) {
     dependsOn(":dist")
     workingDir = rootDir
     systemProperty("kotlin.test.script.classpath", testSourceSet.output.classesDirs.joinToString(File.pathSeparator))