[LC] add isEquivalentTo implementation so LC can be referenced from java

otherwise references from java to ktElements won't be treated as references,
cause java references resolve to light elements and search can/should be called
on ktElements

analysis/symbol-light-classes/testData/equivalentTo/AnnotationClass.kt

@@ -0,0 +1,2 @@
+// org.jetbrains.kotlin.light.classes.symbol.classes.SymbolLightClassForAnnotationClass
+annotation class Fo<caret>oBar

analysis/symbol-light-classes/testData/equivalentTo/AnonymousClass.kt

@@ -0,0 +1,4 @@
+// org.jetbrains.kotlin.light.classes.symbol.classes.SymbolLightClassForAnonymousObject
+val f = obje<caret>ct : I {}
+
+interface I {}

analysis/symbol-light-classes/testData/equivalentTo/CompanionProperty.kt

@@ -0,0 +1,6 @@
+// org.jetbrains.kotlin.light.classes.symbol.fields.SymbolLightFieldForProperty
+class FooBar {
+    companion object {
+        var f<caret>oo : String = ""
+    }
+}

analysis/symbol-light-classes/testData/equivalentTo/Constructor.kt

@@ -0,0 +1,6 @@
+// org.jetbrains.kotlin.light.classes.symbol.methods.SymbolLightConstructor
+class FooBar {
+    cons<caret>tructor() {
+
+    }
+}

analysis/symbol-light-classes/testData/equivalentTo/EnumClassEntry.kt

@@ -0,0 +1,8 @@
+// org.jetbrains.kotlin.light.classes.symbol.classes.SymbolLightClassForEnumEntry
+enum class FooBar {
+    EnumClass<caret>Entry {
+        fun foo() {
+
+        }
+    }
+}

analysis/symbol-light-classes/testData/equivalentTo/Function.kt

@@ -0,0 +1,2 @@
+// org.jetbrains.kotlin.light.classes.symbol.methods.SymbolLightSimpleMethod
+fun foo<caret>Bar() {}

analysis/symbol-light-classes/testData/equivalentTo/Interface.kt

@@ -0,0 +1,2 @@
+// org.jetbrains.kotlin.light.classes.symbol.classes.SymbolLightClassForInterface
+interface Fo<caret>oBar

analysis/symbol-light-classes/testData/equivalentTo/Klass.kt

@@ -0,0 +1,2 @@
+// org.jetbrains.kotlin.light.classes.symbol.classes.SymbolLightClassForClassOrObject
+cl<caret>ass FooBar

analysis/symbol-light-classes/testData/equivalentTo/TypeParameter.kt

@@ -0,0 +1,2 @@
+// org.jetbrains.kotlin.light.classes.symbol.parameters.SymbolLightTypeParameter
+interface FooBar<<caret>T>