[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/low-level-api-fir/testData/contextCollector/scripts/statement.txt

@@ -75,5 +75,5 @@ FILE: [ResolvedTo(IMPORTS)] statement.kts
 
         public? final? [ResolvedTo(RAW_FIR)] fun foo([ResolvedTo(RAW_FIR)] i: Int, [ResolvedTo(RAW_FIR)] action: ( (Int) -> Unit )): R|kotlin/Unit| { LAZY_BLOCK }
 
-        public final [ResolvedTo(RAW_FIR)] val $$result: <implicit> = foo#(LAZY_EXPRESSION, <L> = LAZY_EXPRESSION)
+        public final [ResolvedTo(RAW_FIR)] val $$result: <implicit> = foo#(LAZY_EXPRESSION, LAZY_EXPRESSION)
             public [ResolvedTo(RAW_FIR)] get(): <implicit>