[FIR IDE] Add Fir lightclasses tests and fix FindUsages tests

compiler/testData/asJava/ultraLightClasses/delegatingToInterfaces.java

@@ -0,0 +1,44 @@
+public abstract interface Base /* Base*/ {
+  public abstract int foo(@org.jetbrains.annotations.NotNull() java.lang.String, @org.jetbrains.annotations.Nullable() java.lang.Object);//  foo(java.lang.String, java.lang.Object)
+
+  public abstract int getX();//  getX()
+
+  public abstract int getY();//  getY()
+
+  public abstract void printMessage();//  printMessage()
+
+  public abstract void printMessageLine();//  printMessageLine()
+
+  public abstract void setY(int);//  setY(int)
+
+}
+
+public final class BaseImpl /* BaseImpl*/ implements Base {
+  private final int x;
+
+  public  BaseImpl(int);//  .ctor(int)
+
+  public final int getX();//  getX()
+
+  public void printMessage();//  printMessage()
+
+  public void printMessageLine();//  printMessageLine()
+
+}
+
+public final class Derived /* Derived*/ implements Base {
+  public  Derived(@org.jetbrains.annotations.NotNull() Base);//  .ctor(Base)
+
+  public int foo(@org.jetbrains.annotations.NotNull() java.lang.String, @org.jetbrains.annotations.Nullable() java.lang.Object);//  foo(java.lang.String, java.lang.Object)
+
+  public int getX();//  getX()
+
+  public int getY();//  getY()
+
+  public void printMessage();//  printMessage()
+
+  public void printMessageLine();//  printMessageLine()
+
+  public void setY(int);//  setY(int)
+
+}