[Build] Add jUnit dependencies in testApiJUnit5 to the implementation configuration

Adding these dependencies to the `api` configuration pollutes classpath for each dependant modules even if it doesn't need them. Instead, the dependencies should be declared more granularly if they're required
#KTI-1349 In Progress

libraries/tools/kotlin-main-kts-test/build.gradle.kts

@@ -12,7 +12,7 @@ dependencies {
     testCompileOnly(project(":compiler:cli"))
     testCompileOnly(project(":kotlin-scripting-jvm-host-unshaded"))
     testApi(kotlinStdlib("jdk8"))
-    testApi(libs.junit4)
+    testImplementation(libs.junit4)
     testApi(projectTests(":kotlin-scripting-compiler")) { isTransitive = false }
     testImplementation(project(":kotlin-compiler-embeddable"))
     kotlinxSerializationGradlePluginClasspath(project(":kotlinx-serialization-compiler-plugin.embeddable")) { isTransitive = false }