[IR] Store original function in the IrInlinedBlock

In Native and JS, there is a special logic where the compiler saves
a copy of inlined function (see `InlineFunctionsSupport`). This copy
is used in the IR inliner. Because of that, we can't really compare
inlined function with other functions directly. We need to
get `originalFunction` first and save it.

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UsefulDeclarationProcessor.kt

@@ -57,10 +57,7 @@ abstract class UsefulDeclarationProcessor(
             super.visitBlock(expression, data)
 
             if (expression is IrReturnableBlock) {
-                // We need to extract `originalFunction` here because saved `inlineFunction`
-                // is actually a copy made in `SaveInlineFunctionsBeforeInlining`.
-                // Without this, we are not going to find proper intersection in the `saveOnlyIntersectionOfNextDeclarationsFor` method.
-                expression.inlineFunction?.originalFunction?.addToUsefulPolyfilledDeclarations()
+                expression.inlineFunction?.addToUsefulPolyfilledDeclarations()
             }
         }
 

compiler/ir/ir.inline/src/org/jetbrains/kotlin/ir/inline/FunctionInlining.kt

@@ -162,7 +162,7 @@ class FunctionInlining(
 
         val substituteMap = mutableMapOf<IrValueParameter, IrExpression>()
 
-        fun inline() = inlineFunction(callSite, callee, callee, true)
+        fun inline() = inlineFunction(callSite, callee, callee.originalFunction, true)
 
         private fun <E : IrElement> E.copy(): E {
             @Suppress("UNCHECKED_CAST")