FIR IDE: Begin implementing semantic highlighting via FIR

* Introduce frontend api module & implement api for FIR
* Implement some basic declaration highlighting for FIR

idea/idea-test-framework/test/org/jetbrains/kotlin/idea/test/KotlinLightCodeInsightFixtureTestCase.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -200,13 +200,15 @@ abstract class KotlinLightCodeInsightFixtureTestCase : KotlinLightCodeInsightFix
                 InTextDirectivesUtils.isDirectiveDefined(fileText, "ENABLE_MULTIPLATFORM") ->
                     KotlinProjectDescriptorWithFacet.KOTLIN_STABLE_WITH_MULTIPLATFORM
 
-                else -> KotlinLightProjectDescriptor.INSTANCE
+                else -> getDefaultProjectDescriptor()
             }
         } catch (e: IOException) {
             throw rethrow(e)
         }
     }
 
+    protected open fun getDefaultProjectDescriptor(): KotlinLightProjectDescriptor = KotlinLightProjectDescriptor.INSTANCE
+
     protected fun isAllFilesPresentInTest(): Boolean = KotlinTestUtils.isAllFilesPresentTest(getTestName(false))
 
     protected fun performNotWriteEditorAction(actionId: String): Boolean {