[JS IR] Ignore unbound symbols in IC infrastructure

The IR linker is responsible for detecting unbound symbols,
 if it skips them for some reason, IC infrastructure must not fail
 with unbound symbols exceptions. Anyway, the IR validator
 verifies later if there are unbound symbols in
 reachable IR and generates the corresponding error.

^KT-56602 Fixed

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/IdSignatureSource.kt

@@ -115,7 +115,15 @@ internal sealed class FileSignatureProvider(val irFile: IrFile) {
         }
 
         override fun getImplementedSymbols(): Map<IdSignature, IrSymbol> {
-            return collectImplementedSymbol(fileDeserializer.symbolDeserializer.deserializedSymbols)
+            // Sometimes linker may leave unbound symbols in IrSymbolDeserializer::deserializedSymbols map.
+            // Generally, all unbound symbols must be caught in KotlinIrLinker::checkNoUnboundSymbols,
+            // unfortunately it does not work properly in the current implementation.
+            // Also, reachable unbound symbols are caught by IrValidator, it works fine, but it works after this place.
+            // Filter unbound symbols here, because an error from IC infrastructure about the unbound symbols looks pretty wired
+            // and if the unbound symbol is really reachable from IR the error will be fired from IrValidator later.
+            // Otherwise, the unbound symbol is unreachable, and it cannot appear in IC dependency graph, so we can ignore them.
+            val deserializedSymbols = fileDeserializer.symbolDeserializer.deserializedSymbols.filter { it.value.isBound }
+            return collectImplementedSymbol(deserializedSymbols)
         }
     }