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

compiler/testData/asJava/ultraLightClasses/implementingKotlinCollections.java

@@ -0,0 +1,27 @@
+public final class MyList /* MyList*/ implements java.util.List<java.lang.String>, kotlin.collections.List<java.lang.String>, kotlin.jvm.internal.markers.KMappedMarker {
+  @org.jetbrains.annotations.NotNull()
+  public java.lang.String get(int);//  get(int)
+
+  public  MyList();//  .ctor()
+
+}
+
+public abstract interface ASet /* ASet*/<T>  extends java.util.Collection<T>, kotlin.collections.MutableCollection<T>, kotlin.jvm.internal.markers.KMutableCollection {
+}
+
+public abstract class MySet /* MySet*/<T>  implements ASet<T> {
+  public  MySet();//  .ctor()
+
+  public boolean remove(@org.jetbrains.annotations.NotNull() java.lang.String);//  remove(java.lang.String)
+
+}
+
+public abstract class SmartSet /* SmartSet*/<T>  extends kotlin.collections.AbstractMutableSet<T> {
+  @org.jetbrains.annotations.NotNull()
+  public java.util.Iterator<T> iterator();//  iterator()
+
+  private  SmartSet();//  .ctor()
+
+  public boolean add(T);//  add(T)
+
+}