[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

analysis/analysis-api/testData/components/callResolver/resolveCall/labeledLambda.kt

@@ -0,0 +1,6 @@
+fun foo(l1: (Int) -> Unit) {
+}
+
+fun test() {
+    <expr>foo label@ {}</expr>
+}