IR: minor, add toString to MemberWithOriginal and FakeOverride

To make it easier to debug.

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/overrides/IrFakeOverrideBuilder.kt

@@ -35,7 +35,9 @@ class IrFakeOverrideBuilder(
 ) {
     private val overrideChecker = IrOverrideChecker(typeSystem, externalOverridabilityConditions)
 
-    internal data class FakeOverride(val override: IrOverridableMember, val original: IrOverridableMember)
+    internal data class FakeOverride(val override: IrOverridableMember, val original: IrOverridableMember) {
+        override fun toString(): String = override.render()
+    }
 
     private var IrOverridableMember.overriddenSymbols: List<IrSymbol>
         get() = when (this) {

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/overrides/IrOverrideChecker.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.ir.overrides.IrExternalOverridabilityCondition.Resul
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContext
 import org.jetbrains.kotlin.ir.types.IrTypeSystemContextWithAdditionalAxioms
 import org.jetbrains.kotlin.ir.types.createIrTypeCheckerState
+import org.jetbrains.kotlin.ir.util.render
 import org.jetbrains.kotlin.resolve.OverridingUtil.OverrideCompatibilityInfo
 import org.jetbrains.kotlin.resolve.OverridingUtil.OverrideCompatibilityInfo.*
 import org.jetbrains.kotlin.types.AbstractTypeChecker
@@ -25,6 +26,8 @@ class MemberWithOriginal(val member: IrOverridableMember, original: IrOverridabl
     internal constructor(fakeOverride: IrFakeOverrideBuilder.FakeOverride) : this(fakeOverride.override, fakeOverride.original)
 
     val original: IrOverridableMember = original ?: member
+
+    override fun toString(): String = member.render()
 }
 
 class IrOverrideChecker(