Sort out blackBox*() methods

- get rid of blackBox(), extract tests into files
- delete single-file usages of blackBoxMultiFile()
- inline some other blackBox methods
- suppress exception in blackBoxWithJava()

compiler/testData/codegen/classes/classObjectField.kt

@@ -0,0 +1,7 @@
+class A() {
+    class object {
+        val value = 10
+    }
+}
+
+fun box() = if (A.value == 10) "OK" else "Fail ${A.value}"