[FIR] Fix top-level property initialization checks in scripts

- While `collectionInitializationInfo` unwrapped a script's top-level
  declarations, `check` forgot to do it, so a script effectively had no
  top-level properties in the mind of the checker.

^KT-63286 fixed

compiler/testData/diagnostics/tests/script/topLevelPropertyInitialization.fir.kts

@@ -32,9 +32,9 @@ val d: String by simpleDelegate(d)
 val e: String by inPlaceDelegate { e }
 val f: String by notInPlaceDelegate { f }
 
-val g: Int
+<!MUST_BE_INITIALIZED!>val g: Int<!>
 val h = 1.also { <!VAL_REASSIGNMENT!>g<!> = 2 }
-val i: Int
+<!MUST_BE_INITIALIZED!>val i: Int<!>
 val j by lazy { <!VAL_REASSIGNMENT!>i<!> = 2; 1 }
 val k: Int
     get() {