Revert "[FIR] Let attributes opt-in to participating in ConeClassLikeTypeImpl structural equality"

This reverts commit 9189154cae.

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeAttributes.kt

@@ -32,13 +32,6 @@ abstract class ConeAttribute<out T : ConeAttribute<T>> : AnnotationMarker {
     abstract override fun toString(): String
     open fun renderForReadability(): String? = null
 
-    /**
-     * Signals that this attribute properly implements the [equals] and [hashCode] protocol.
-     *
-     * If it returns `true`, attributes will be compared using structural equality in [ConeAttributes.definitelyDifferFrom].
-     */
-    open val implementsEquality: Boolean get() = false
-
     abstract val key: KClass<out T>
 
     /**
@@ -159,32 +152,6 @@ class ConeAttributes private constructor(attributes: List<ConeAttribute<*>>) : A
         return create(attributes)
     }
 
-    /**
-     * Returns `true` if this instance is definitely not equal to the [other] instance.
-     * This is `true` when one instance contains an attribute **type** that the other doesn't contain or both instances contain
-     * an attribute of a type where [ConeAttribute.implementsEquality]` == true` and the attribute's [equals] method returns `false`.
-     *
-     * A return value of `false` doesn't guarantee that the instances are equal because [ConeAttribute.implementsEquality] is optional,
-     * i.e., not all attributes can be compared structurally.
-     *
-     * @see org.jetbrains.kotlin.fir.types.impl.ConeClassLikeTypeImpl.equals
-     */
-    infix fun definitelyDifferFrom(other: ConeAttributes): Boolean {
-        if (this === other) return false
-        if (this.isEmpty() && other.isEmpty()) return false
-
-        for (index in indices) {
-            val a = arrayMap[index]
-            val b = other.arrayMap[index]
-
-            if (a == null && b == null) continue
-            if ((a == null) != (b == null)) return true
-            if (a!!.implementsEquality && a != b) return true
-        }
-
-        return false
-    }
-
     /**
      * Applies the [transform] to all attributes that are subtypes of [ConeAttributeWithConeType] and returns a [ConeAttributes]
      * with the results of transforms that were not-`null` or `null` if no attributes were transformed.

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/impl/Impl.kt

@@ -34,7 +34,6 @@ class ConeClassLikeTypeImpl(
         if (lookupTag != other.lookupTag) return false
         if (!typeArguments.contentEquals(other.typeArguments)) return false
         if (nullability != other.nullability) return false
-        if (attributes definitelyDifferFrom other.attributes) return false
 
         return true
     }