[light classes] Improve isEquivalence checks

^KTIJ-25412

Update equivalence checks for light accessor methods and light fields
 to make them equivalent if they share the same underlying property.
 Follow the `kotlinOrigin` declaration:
 even if there is a property accessor,
 use property declaration.

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

@@ -0,0 +1,6 @@
+// org.jetbrains.kotlin.light.classes.symbol.fields.SymbolLightFieldForProperty
+class FooBar {
+    var f<caret>oo : String = "42"
+            get() = "42"
+    
+}