[FIR] Remove FirLambdaArgumentExpression

It's not really necessary if the information about if the lambda was a
trailing lambda can be directly saved in FirAnonymousFunctionExpression.

Removing the FIR node uncovered a couple of bugs
(UNINITIALIZED_ENUM_ENTRY, ERROR_IN_CONTRACT_DESCRIPTION) that were
caused by assuming that a lambda is always a trailing lambda.

#KT-66124

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirExpressionBuilder.kt

@@ -1513,9 +1513,9 @@ class LightTreeRawFirExpressionBuilder(
                 VALUE_ARGUMENT -> container += convertValueArgument(node)
                 LAMBDA_EXPRESSION,
                 LABELED_EXPRESSION,
-                ANNOTATED_EXPRESSION -> container += buildLambdaArgumentExpression {
-                    source = valueArguments.toFirSourceElement()
-                    expression = getAsFirExpression(node)
+                ANNOTATED_EXPRESSION,
+                -> container += getAsFirExpression<FirAnonymousFunctionExpression>(node).apply {
+                    replaceIsTrailingLambda(newIsTrailingLambda = true)
                 }
             }
         }