Use mock JDK in compiler tests where full JDK is not needed

- move some of boxWithStdlib tests under fullJdk/ directory, where they will be
  compiled against the full JDK
- introduce FULL_JDK in-text directive for the reflection test as only 4 tests
  out of 654 needed the full JDK

compiler/testData/loadJava/compiledJava/modality/ModalityOfFakeOverrides.java

@@ -1,3 +1,4 @@
+// FULL_JDK
 package test;
 
 import org.jetbrains.annotations.NotNull;