[JS IR BE] Enable unconditional validation

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt

@@ -66,6 +66,18 @@ private fun makeCustomJsModulePhase(
     }
 )
 
+private val validateIrBeforeLowering = makeCustomJsModulePhase(
+    { context, module -> validationCallback(context, module) },
+    name = "ValidateIrBeforeLowering",
+    description = "Validate IR before lowering"
+)
+
+private val validateIrAfterLowering = makeCustomJsModulePhase(
+    { context, module -> validationCallback(context, module) },
+    name = "ValidateIrAfterLowering",
+    description = "Validate IR after lowering"
+)
+
 private val moveBodilessDeclarationsToSeparatePlacePhase = makeCustomJsModulePhase(
     { context, module ->
         moveBodilessDeclarationsToSeparatePlace(context, module)
@@ -357,7 +369,8 @@ private val staticMembersLoweringPhase = makeJsModulePhase(
 val jsPhases = namedIrModulePhase(
     name = "IrModuleLowering",
     description = "IR module lowering",
-    lower = testGenerationPhase then
+    lower = validateIrBeforeLowering then
+            testGenerationPhase then
             expectDeclarationsRemovingPhase then
             arrayConstructorPhase then
             functionInliningPhase then
@@ -399,5 +412,6 @@ val jsPhases = namedIrModulePhase(
             primitiveCompanionLoweringPhase then
             constLoweringPhase then
             callsLoweringPhase then
-            staticMembersLoweringPhase
+            staticMembersLoweringPhase then
+            validateIrAfterLowering
 )