Make fast class files reading mode default in compiler tests

This makes sense because this mode is the default in the production
compiler. Forgetting to enable it where necessary led to different
bizarre test failures, see for example changes around 3fee84b966 and
KT-34826

plugins/uast-kotlin/tests/AbstractKotlinUastTest.kt

@@ -106,11 +106,11 @@ abstract class AbstractKotlinUastTest : AbstractUastTest() {
     override fun createEnvironment(source: File): AbstractCoreEnvironment {
         val appWasNull = ApplicationManager.getApplication() == null
         compilerConfiguration = createKotlinCompilerConfiguration(source)
+        compilerConfiguration.put(JVMConfigurationKeys.USE_PSI_CLASS_FILES_READING, true)
+
         val parentDisposable = Disposer.newDisposable()
-        val kotlinCoreEnvironment = KotlinCoreEnvironment.createForTests(
-                parentDisposable,
-                compilerConfiguration,
-                EnvironmentConfigFiles.JVM_CONFIG_FILES)
+        val kotlinCoreEnvironment =
+            KotlinCoreEnvironment.createForTests(parentDisposable, compilerConfiguration, EnvironmentConfigFiles.JVM_CONFIG_FILES)
 
         this.kotlinCoreEnvironment = kotlinCoreEnvironment