FIR: in case of smart cast, use original type for FirThisRcvrExpression

Before this commit, we used type after smart cast both for original
FirThisReceiverExpression and for wrapping FirExpressionWithSmartCast.
However, this makes FIR2IR implicit cast generator work incorrectly
(it decides not to insert implicit cast because original type is the same).
After this commit, expressions have different types and implicit cast
generator works properly.

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/FirReceivers.kt

@@ -67,6 +67,8 @@ sealed class ImplicitReceiverValue<S : AbstractFirBasedSymbol<*>>(
     final override var type: ConeKotlinType = type
         private set
 
+    val originalType: ConeKotlinType = type
+
     var implicitScope: FirTypeScope? = type.scope(useSiteSession, scopeSession, FakeOverrideTypeCalculator.DoNothing)
         private set
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt

@@ -78,7 +78,7 @@ open class FirExpressionsResolveTransformer(transformer: FirBodyResolveTransform
                 implicitReceiver?.boundSymbol?.let {
                     callee.replaceBoundSymbol(it)
                 }
-                val implicitType = implicitReceiver?.type
+                val implicitType = implicitReceiver?.originalType
                 qualifiedAccessExpression.resultType = when {
                     implicitReceiver is InaccessibleImplicitReceiverValue -> buildErrorTypeRef {
                         source = qualifiedAccessExpression.source